System and method using impulse radio technology to track and monitor people under house arrest

ABSTRACT

A system, electronic monitor and method are provided that utilize the capabilities of impulse radio technology to overcome the shortcomings of conventional house arrest monitoring systems. One embodiment of the present invention enables monitoring personnel (e.g., police officers, parole officers) to determine whether a person under house arrest and carrying an electronic monitor stays within their home. Another embodiment of the present invention enables monitoring personnel to determine whether a person under house arrest and carrying an electronic monitor is located within their home and/or also enables monitoring personnel to monitor the vital signs of that person.

CROSS REFERENCE TO COPENDING APPLICATIONS

This application is a Continuation-In-Part to two U.S. Applications oneof which was filed on Sep. 27, 1999 and entitled “System and Method forMonitoring Assets, Objects, People and Animals Utilizing Impulse Radio”(U.S. Ser. No. 09/407,106) and the other was filed on Dec. 8, 1999 andentitled “System and Method for Person or Object Position LocationUtilizing Impulse Radio” (U.S. Ser. No. 09/456,409, now U.S. Pat. No.6,300,903 which is a Continuation-In-Part of the U.S. application Ser.No. 09/045,929, which was filed on Mar. 23, 1998 now U.S. Pat. No.6,133,876) which are incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates in general to the home confinement fieldand, in particular, to a system and method capable of using impulseradio technology to track and monitor people under house arrest.

2. Description of Related Art

The number of people incarcerated in prison has increased dramaticallyin the past few years, resulting in overcrowded prisons that aredifficult and costly to operate and maintain. This troublesome situationhas led many local and state governments to alternative forms ofsentencing and detention including house arrest wherein a person isconfined in their house or apartment instead of being confined in aprison.

In general, a person under house arrest is required to wear anelectronic monitor. The electronic monitor often includes a radiotransmitter, which transmits radio signals to a radio receiver connectedto a telephone at the person's home. The telephone can be programmed tocall a central station manned by monitoring personnel whenever the radioreceiver fails to receive the radio signal from the electronic monitor.However, problems have arisen in the past with this scenario becausewith standard radio transmissions there are often problematical “deadzones” within a home that may trigger a false alarm.

The “dead zones” can be attributable to the closed structure of thehome, which can make it difficult for a standard radio transmitter tomaintain contact with a standard radio receiver as the person carryingthe standard radio transmitter moves through the home. For instance, thecentral station may receive a false alarm that the electronic monitor(including a standard radio transmitter) secured to the person underhouse arrest is no longer communicating to the standard radio receivereven though the person is still in the home. In particular, the falsealarm may be triggered because the standard radio signals sent from thestandard radio transmitter cannot penetrate a certain wall or floorwithin the home and reach the standard radio receiver.

In addition, the “dead zones” may be attributable to multipathinterference which can be very problematic in a closed structure such asa home. Multipath interference is an error caused by the interference ofa standard radio signal that has reached a standard radio receiver bytwo or more paths. Essentially, the standard radio receiver may not beable to demodulate the standard radio signal because the transmittedradio signal effectively cancels itself out by bouncing of walls andfloors before reaching the standard radio receiver. Accordingly, therehas been a persistent need to develop a system, electronic monitor andmethod that can effectively track and monitor people that are confinedto their homes.

BRIEF DESCRIPTION OF THE INVENTION

The present invention includes a system, electronic monitor and methodthat utilize the capabilities of impulse radio technology to overcomethe shortcomings of conventional house arrest monitoring systems. Oneembodiment of the present invention enables monitoring personnel (e.g.,police officers, parole officers) to determine whether a person underhouse arrest and carrying an electronic monitor stays within their home.Another embodiment of the present invention enables monitoring personnelto determine whether a person under house arrest and carrying anelectronic monitor is located within their home and/or also enablesmonitoring personnel to monitor the vital signs of that person.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention may be had byreference to the following detailed description when taken inconjunction with the accompanying drawings wherein:

FIG. 1A illustrates a representative Gaussian Monocycle waveform in thetime domain.

FIG. 1B illustrates the frequency domain amplitude of the GaussianMonocycle of FIG. 1A.

FIG. 2A illustrates a pulse train comprising pulses as in FIG. 1A.

FIG. 2B illustrates the frequency domain amplitude of the waveform ofFIG. 2A.

FIG. 3 illustrates the frequency domain amplitude of a sequence of timecoded pulses.

FIG. 4 illustrates a typical received signal and interference signal.

FIG. 5A illustrates a typical geometrical configuration giving rise tomultipath received signals.

FIG. 5B illustrates exemplary muitipath signals in the time domain.

FIGS. 5C-5E illustrate a signal plot of various multipath environments.

FIG. 5F illustrates a plurality of multipaths with a plurality ofreflectors from a transmitter to a receiver.

FIG. 5G graphically represents signal strength as volts vs. time in adirect path and multipath environment.

FIG. 6 illustrates representative impulse radio transmitter functionaldiagram.

FIG. 7 illustrates a representative impulse radio receiver functionaldiagram.

FIG. 8A illustrates a representative received pulse signal at the inputto the correlator.

FIG. 8B illustrates a sequence of representative impulse signals in thecorrelation process.

FIG. 8C illustrates the output of the correlator for each of the timeoffsets of FIG. 8E.

FIG. 9 is a diagram illustrating the basic components of a firstembodiment of a system in accordance with the present invention.

FIG. 10 is a diagram illustrating in greater detail an electronicmonitor of the system shown in FIG. 9.

FIG. 11 is a flowchart illustrating the basic steps of a preferredmethod for tracking a person under house arrest in accordance with thefirst embodiment of the present invention.

FIG. 12 is a diagram illustrating the basic components of a secondembodiment of the system in accordance with the present invention.

FIG. 13 is a diagram illustrating in greater detail an electronicmonitor of the system shown in FIG. 12.

FIG. 14 is a diagram illustrating a Global Positioning System (GPS)based option and a work place option that can be incorporated within thesystem shown in FIG. 12.

FIG. 15 is a flowchart illustrating the basic steps of a preferredmethod for tracking and monitoring a person under house arrest inaccordance with the second embodiment of the present invention.

FIG. 16 is a block diagram of an impulse radio positioning networkutilizing a synchronized transceiver tracking architecture that can beused in the present invention.

FIG. 17 is a block diagram of an impulse radio positioning networkutilizing an unsynchronized transceiver tracking architecture that canbe used in the present invention.

FIG. 18 is a block diagram of an impulse radio positioning networkutilizing a synchronized transmitter tracking architecture that can beused in the present invention.

FIG. 19 is a block diagram of an impulse radio positioning networkutilizing an unsynchronized transmitter tracking architecture that canbe used in the present invention.

FIG. 20 is a block diagram of an impulse radio positioning networkutilizing a synchronized receiver tracking architecture that can be usedin the present invention.

FIG. 21 is a block diagram of an impulse radio positioning networkutilizing an unsynchronized receiver tracking architecture that can beused in the present invention.

FIG. 22 is a diagram of an impulse radio positioning network utilizing amixed mode reference radio tracking architecture that can be used in thepresent invention.

FIG. 23 is a diagram of an impulse radio positioning network utilizing amixed mode mobile apparatus tracking architecture that can be used inthe present invention.

FIG. 24 is a diagram of a steerable null antennae architecture capableof being used in an impulse radio positioning network in accordance thepresent invention.

FIG. 25 is a diagram of a specialized difference antennae architecturecapable of being used in an impulse radio positioning network inaccordance the present invention.

FIG. 26 is a diagram of a specialized directional antennae architecturecapable of being used in an impulse radio positioning network inaccordance with the present invention.

FIG. 27 is a diagram of an amplitude sensing architecture capable ofbeing used in an impulse radio positioning network in accordance withthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention includes a system, electronic monitor and methodcapable using impulse radio technology to track and/or monitor a personunder house arrest. The use of impulse radio technology to help trackand/or monitor people confined to their homes is a significantimprovement over the state-of-art. This significant improvement over thestate-of-art is attributable, in part, to the use of an emerging,revolutionary ultra wideband technology (UWB) called impulse radiocommunication technology (also known as impulse radio).

Impulse radio was first fully described in a series of patents,including U.S. Pat. No. 4,641,317 (issued Feb. 3, 1987), U.S. Pat. No.4,813,057 (issued Mar. 14, 1989), U.S. Pat. No. 4,979,186 (issued Dec.18, 1990) and U.S. Pat. No. 5,363,108 (issued Nov. 8, 1994) to Larry W.Fullerton. A second generation of impulse radio patents includes U.S.Pat. No. 5,677,927 (issued Oct. 14, 1997), U.S. Pat. No. 5,687,169(issued Nov. 11, 1997) and co-pending application Ser. No. 08/761,602(filed Dec. 6, 1996) to Fullerton et al.

Uses of impulse radio systems are described in U.S. patent applicationSer. No. 09/332,502, entitled, “System and Method for IntrusionDetection using a Time Domain Radar Array” and U.S. patent applicationSer. No. 09/332,503, entitled, “Wide Area Time Domain Radar Array” bothfiled on Jun. 14, 1999 and both of which are assigned to the assignee ofthe present invention. These patent documents are incorporated herein byreference.

Impulse Radio Basics

Impulse radio refers to a radio system based on short, low duty cyclepulses. An ideal impulse radio waveform is a short Gaussian monocycle.As the name suggests, this waveform attempts to approach one cycle ofradio frequency (RF) energy at a desired center frequency. Due toimplementation and other spectral limitations, this waveform may bealtered significantly in practice for a given application. Mostwaveforms with enough bandwidth approximate a Gaussian shape to a usefuldegree.

Impulse radio can use many types of modulation, including AM, time shift(also referred to as pulse position) and M-ary versions. The time shiftmethod has simplicity and power output advantages that make itdesirable. In this document, the time shift method is used as anillustrative example.

In impulse radio communications, the pulse-to-pulse interval can bevaried on a pulse-by-pulse basis by two components: an informationcomponent and a code component. Generally, conventional spread spectrumsystems employ codes to spread the normally narrow band informationsignal over a relatively wide band of frequencies. A conventional spreadspectrum receiver correlates these signals to retrieve the originalinformation signal. Unlike conventional spread spectrum systems, inimpulse radio communications codes are not needed for energy spreadingbecause the monocycle pulses themselves have an inherently widebandwidth. Instead, codes are used for channelization, energy smoothingin the frequency domain, resistance to interference, and reducing theinterference potential to nearby receivers.

The impulse radio receiver is typically a direct conversion receiverwith a cross correlator front end which coherently converts anelectromagnetic pulse train of monocycle pulses to a baseband signal ina single stage. The baseband signal is the basic information signal forthe impulse radio communications system. It is often found desirable toinclude a subcarrier with the baseband signal to help reduce the effectsof amplifier drift and low frequency noise. The subcarrier that istypically implemented alternately reverses modulation according to aknown pattern at a rate faster than the data rate. This same pattern isused to reverse the process and restore the original data pattern justbefore detection. This method permits alternating current (AC) couplingof stages, or equivalent signal processing to eliminate direct current(DC) drift and errors from the detection process. This method isdescribed in detail in U.S. Pat. No. 5,677,927 to Fullerton et al.

In impulse radio communications utilizing time shift modulation, eachdata bit typically time position modulates many pulses of the periodictiming signal. This yields a modulated, coded timing signal thatcomprises a train of pulses for each single data bit. The impulse radioreceiver integrates multiple pulses to recover the transmittedinformation.

Waveforms

Impulse radio refers to a radio system based on short, low duty cyclepulses. In the widest bandwidth embodiment, the resulting waveformapproaches one cycle per pulse at the center frequency. In more narrowband embodiments, each pulse consists of a burst of cycles usually withsome spectral shaping to control the bandwidth to meet desiredproperties such as out of band emissions or in-band spectral flatness,or time domain peak power or burst off time attenuation.

For system analysis purposes, it is convenient to model the desiredwaveform in an ideal sense to provide insight into the optimum behaviorfor detail design guidance. One such waveform model that has been usefulis the Gaussian monocycle as shown in FIG. 1A. This waveform isrepresentative of the transmitted pulse produced by a step function intoan ultra-wideband antenna. The basic equation normalized to a peak valueof 1 is as follows:${f_{mono}(t)} = {\sqrt{}\left( \frac{t}{\sigma} \right)^{\frac{- t^{2}}{2\quad \sigma^{2}}}}$

Where,

σ is a time scaling parameter,

t is time,

f_(mono)(t) is the waveform voltage, and

e is the natural logarithm base.

The frequency domain spectrum of the above waveform is shown in FIG. 1B.The corresponding equation is:

F _(mono)(f)=(2π)^(3/2) σfe ^(−2(πσf)) ²

The center frequency (f_(c)), or frequency of peak spectral density is:$f_{c} = \frac{1}{2\quad \pi \quad \sigma}$

These pulses, or bursts of cycles, may be produced by methods describedin the patents referenced above or by other methods that are known toone of ordinary skill in the art. Any practical implementation willdeviate from the ideal mathematical model by some amount. In fact, thisdeviation from ideal may be substantial and yet yield a system withacceptable performance. This is especially true for microwaveimplementations, where precise waveform shaping is difficult to achieve.These mathematical models are provided as an aid to describing idealoperation and are not intended to limit the invention. In fact, anyburst of cycles that adequately fills a given bandwidth and has anadequate on-off attenuation ratio for a given application will serve thepurpose of this invention.

A Pulse Train

Impulse radio systems can deliver one or more data bits per pulse;however, impulse radio systems more typically use pulse trains, notsingle pulses, for each data bit. As described in detail in thefollowing example system, the impulse radio transmitter produces andoutputs a train of pulses for each bit of information.

Prototypes have been built which have pulse repetition frequenciesincluding 0.7 and 10 megapulses per second (Mpps, where each megapulseis 10⁶ pulses). FIGS. 2A and 2B are illustrations of the output of atypical 10 Mpps system with uncoded, unmodulated, 0.5 nanosecond (ns)pulses 102. FIG. 2A shows a time domain representation of this sequenceof pulses 102. FIG. 2B, which shows 60 MHZ at the center of the spectrumfor the waveform of FIG. 2A, illustrates that the result of the pulsetrain in the frequency domain is to produce a spectrum comprising a setof lines 204 spaced at the frequency of the 10 Mpps pulse repetitionrate. When the full spectrum is shown, the envelope of the line spectrumfollows the curve of the single pulse spectrum 104 of FIG. 1B. For thissimple uncoded case, the power of the pulse train is spread amongroughly two hundred comb lines. Each comb line thus has a small fractionof the total power and presents much less of an interference problem toa receiver sharing the band.

It can also be observed from FIG. 2A that impulse radio systemstypically have very low average duty cycles resulting in average powersignificantly lower than peak power. The duty cycle of the signal in thepresent example is 0.5%, based on a 0.5 ns pulse in a 100 ns interval.

Coding for Energy Smoothing and Channelization

For high pulse rate systems, it may be necessary to more finely spreadthe spectrum than is achieved by producing comb lines. This may be doneby non-uniformly positioning each pulse relative to its nominal positionaccording to a code such as a pseudo random code.

FIG. 3 is a plot illustrating the impact of a pseudo-noise (PN) codedither on energy distribution in the frequency domain (A pseudo-noise,or PN code is a set of time positions defining pseudo-random positioningfor each pulse in a sequence of pulses). FIG. 3, when compared to FIG.2B, shows that the impact of using a PN code is to destroy the comb linestructure and spread the energy more uniformly. This structure typicallyhas slight variations that are characteristic of the specific code used.

Coding also provides a method of establishing independent communicationchannels using impulse radio. Codes can be designed to have low crosscorrelation such that a pulse train using one code will seldom collideon more than one or two pulse positions with a pulses train usinganother code during any one data bit time. Since a data bit may comprisehundreds of pulses, this represents a substantial attenuation of theunwanted channel.

Modulation

Any aspect of the waveform can be modulated to convey information.Amplitude modulation, phase modulation, frequency modulation, time shiftmodulation and M-ary versions of these have been proposed. Both analogand digital forms have been implemented. of these, digital time shiftmodulation has been demonstrated to have various advantages and can beeasily implemented using a correlation receiver architecture.

Digital time shift modulation can be implemented by shifting the codedtime position by an additional amount (that is, in addition to codedither) in response to the information signal. This amount is typicallyvery small relative to the code shift. In a 10 Mpps system with a centerfrequency of 2 GHz., for example, the code may command pulse positionvariations over a range of 100 ns; whereas, the information modulationmay only deviate the pulse position by 150 ps.

Thus, in a pulse train of n pulses, each pulse is delayed a differentamount from its respective time base clock position by an individualcode delay amount plus a modulation amount, where n is the number ofpulses associated with a given data symbol digital bit.

Modulation further smooths the spectrum, minimizing structure in theresulting spectrum.

Reception and Demodulation

Clearly, if there were a large number of impulse radio users within aconfined area, there might be mutual interference. Further, while codingminimizes that interference, as the number of users rises, theprobability of an individual pulse from one user's sequence beingreceived simultaneously with a pulse from another user's sequenceincreases. Impulse radios are able to perform in these environments, inpart, because they do not depend on receiving every pulse. The impulseradio receiver performs a correlating, synchronous receiving function(at the RF level) that uses a statistical sampling and combining of manypulses to recover the transmitted information.

Impulse radio receivers typically integrate from 1 to 1000 or morepulses to yield the demodulated output. The optimal number of pulsesover which the receiver integrates is dependent on a number ofvariables, including pulse rate, bit rate, interference levels, andrange.

Interference Resistance

Besides channelization and energy smoothing, coding also makes impulseradios highly resistant to interference from all radio communicationssystems, including other impulse radio transmitters. This is critical asany other signals within the band occupied by an impulse signalpotentially interfere with the impulse radio. Since there are currentlyno unallocated bands available for impulse systems, they must sharespectrum with other conventional radio systems without being adverselyaffected. The code helps impulse systems discriminate between theintended impulse transmission and interfering transmissions from others.

FIG. 4 illustrates the result of a narrow band sinusoidal interferencesignal 402 overlaying an impulse radio signal 404. At the impulse radioreceiver, the input to the cross correlation would include the narrowband signal 402, as well as the received ultrawide-band impulse radiosignal 404. The input is sampled by the cross correlator with a codedithered template signal 406. Without coding, the cross correlationwould sample the interfering signal 402 with such regularity that theinterfering signals could cause significant interference to the impulseradio receiver. However, when the transmitted impulse signal is encodedwith the code dither (and the impulse radio receiver template signal 406is synchronized with that identical code dither) the correlation samplesthe interfering signals non-uniformly. The samples from the interferingsignal add incoherently, increasing roughly according to square root ofthe number of samples integrated; whereas, the impulse radio samples addcoherently, increasing directly according to the number of samplesintegrated. Thus, integrating over many pulses overcomes the impact ofinterference.

Processing Gain

Impulse radio is resistant to interference because of its largeprocessing gain. For typical spread spectrum systems, the definition ofprocessing gain, which quantifies the decrease in channel interferencewhen wide-band communications are used, is the ratio of the bandwidth ofthe channel to the bit rate of the information signal. For example, adirect sequence spread spectrum system with a 10 KHz informationbandwidth and a 10 MHz channel bandwidth yields a processing gain of1000 or 30 dB. However, far greater processing gains are achieved byimpulse radio systems, where the same 10 KHz information bandwidth isspread across a much greater 2 GHz channel bandwidth, resulting in atheoretical processing gain of 200,000 or 53 dB.

Capacity

It has been shown theoretically, using signal to noise arguments, thatthousands of simultaneous voice channels are available to an impulseradio system as a result of the exceptional processing gain, which isdue to the exceptionally wide spreading bandwidth.

For a simplistic user distribution, with N interfering users of equalpower equidistant from the receiver, the total interference signal tonoise ratio as a result of these other users can be described by thefollowing equation: $V_{tot}^{2} = \frac{N\quad \sigma^{2}}{\sqrt{Z}}$

Where

V² _(tot) is the total interference signal to noise ratio variance, atthe receiver;

N is the number of interfering users;

σ² is the signal to noise ratio variance resulting from one of theinterfering signals with a single pulse cross correlation; and

Z is the number of pulses over which the receiver integrates to recoverthe modulation.

This relationship suggests that link quality degrades gradually as thenumber of simultaneous users increases. It also shows the advantage ofintegration gain. The number of users that can be supported at the sameinterference level increases by the square root of the number of pulsesintegrated.

Multipath and Propagation

One of the striking advantages of impulse radio is its resistance tomultipath fading effects. Conventional narrow band systems are subjectto multipath through the Rayleigh fading process, where the signals frommany delayed reflections combine at the receiver antenna according totheir seemingly random relative phases. This results in possiblesummation or possible cancellation, depending on the specificpropagation to a given location. This situation occurs where the directpath signal is weak relative to the multipath signals, which representsa major portion of the potential coverage of a radio system. In mobilesystems, this results in wild signal strength fluctuations as a functionof distance traveled, where the changing mix of multipath signalsresults in signal strength fluctuations for every few feet of travel.

Impulse radios, however, can be substantially resistant to theseeffects. Impulses arriving from delayed multipath reflections typicallyarrive outside of the correlation time and thus can be ignored. Thisprocess is described in detail with reference to FIGS. 5A and 5B. InFIG. 5A, three propagation paths are shown. The direct path representingthe straight-line distance between the transmitter and receiver is theshortest. Path 1 represents a grazing multipath reflection, which isvery close to the direct path. Path 2 represents a distant multipathreflection. Also shown are elliptical (or, in space, ellipsoidal) tracesthat represent other possible locations for reflections with the sametime delay.

FIG. 5B represents a time domain plot of the received waveform from thismultipath propagation configuration. This figure comprises three doubletpulses as shown in FIG. 1A. The direct path signal is the referencesignal and represents the shortest propagation time. The path 1 signalis delayed slightly and actually overlaps and enhances the signalstrength at this delay value. Note that the reflected waves are reversedin polarity. The path 2 signal is delayed sufficiently that the waveformis completely separated from the direct path signal. If the correlatortemplate signal is positioned at the direct path signal, the path 2signal will produce no response. It can be seen that only the multipathsignals resulting from very close reflectors have any effect on thereception of the direct path signal. The multipath signals delayed lessthan one quarter wave (one quarter wave is about 1.5 inches, or 3.5 cmat 2 GHz center frequency) are the only multipath signals that canattenuate the direct path signal. This region is equivalent to the firstFresnel zone familiar to narrow band systems designers. Impulse radio,however, has no further nulls in the higher Fresnel zones. The abilityto avoid the highly variable attenuation from multipath gives impulseradio significant performance advantages.

FIG. 5A illustrates a typical multipath situation, such as in abuilding, where there are many reflectors 5A04, 5A05 and multiplepropagation paths 5A02, 5A01. In this figure, a transmitter TX 5A06transmits a signal that propagates along the multiple propagation paths5A02, 5A04 to receiver RX 5A08, where the multiple reflected signals arecombined at the antenna.

FIG. 5B illustrates a resulting typical received composite pulsewaveform resulting from the multiple reflections and multiplepropagation paths 5A01, 5A02. In this figure, the direct path signal5A01 is shown as the first pulse signal received. The multiple reflectedsignals (“multipath signals”, or “multipath”) comprise the remainingresponse as illustrated.

FIGS. 5C, 5D, and 5E represent the received signal from a TM-UWBtransmitter in three different multipath environments. These figures arenot actual signal plots, but are hand drawn plots approximating typicalsignal plots. FIG. 5C illustrates the received signal in a very lowmultipath environment. This may occur in a building where the receiverantenna is in the middle of a room and is one meter from thetransmitter. This may also represent signals received from somedistance, such as 100 meters, in an open field where there are noobjects to produce reflections. In this situation, the predominant pulseis the first received pulse and the multipath reflections are too weakto be significant. FIG. 5D illustrates an intermediate multipathenvironment. This approximates the response from one room to the next ina building. The amplitude of the direct path signal is less than in FIG.5C and several reflected signals are of significant amplitude. FIG. 5Eapproximates the response in a severe multipath environment such as:propagation through many rooms; from corner to corner in a building;within a metal cargo hold of a ship; within a metal truck trailer; orwithin an intermodal shipping container. In this scenario, the main pathsignal is weaker than in FIG. 5D. In this situation, the direct pathsignal power is small relative to the total signal power from thereflections.

An impulse radio receiver can receive the signal and demodulate theinformation using either the direct path signal or any multipath signalpeak having sufficient signal to noise ratio. Thus, the impulse radioreceiver can select the strongest response from among the many arrivingsignals. In order for the signals to cancel and produce a null at agiven location, dozens of reflections would have to be cancelledsimultaneously and precisely while blocking the direct path—a highlyunlikely scenario. This time separation of mulitipath signals togetherwith time resolution and selection by the receiver permit a type of timediversity that virtually eliminates cancellation of the signal. In amultiple correlator rake receiver, performance is further improved bycollecting the signal power from multiple signal peaks for additionalsignal to noise performance.

Where the system of FIG. 5A is a narrow band system and the delays aresmall relative to the data bit time, the received signal is a sum of alarge number of sine waves of random amplitude and phase. In theidealized limit, the resulting envelope amplitude has been shown tofollow a Rayleigh probability distribution as follows:${p(r)} = {\frac{1}{\sigma^{2}}{\exp \left( \frac{- r^{2}}{2\quad \sigma^{2}} \right)}}$

where

r is the envelope amplitude of the combined multipath signals, and

2σ² is the RMS power of the combined multipath signals.

In a high multipath environment such as inside homes, offices,warehouses, automobiles, trailers, shipping containers, or outside inthe urban canyon or other situations where the propagation is such thatthe received signal is primarily scattered energy, impulse radio,according to the present invention, can avoid the Rayleigh fadingmechanism that limits performance of narrow band systems. This isillustrated in FIGS. 5F and 5G in a transmit and receive system in ahigh multipath environment 5F00, wherein the transmitter 5F06 transmitsto receiver 5F08 with the signals reflecting off reflectors 5F03 whichform multipaths 5F02. The direct path is illustrated as 5FO1 with thesignal graphically illustrated at 5G02, with the vertical axis being thesignal strength in volts and horizontal axis representing time innanoseconds. Multipath signals are graphically illustrated at 5G04.

Distance Measurement

Important for positioning, impulse systems can measure distances toextremely fine resolution because of the absence of ambiguous cycles inthe waveform. Narrow band systems, on the other hand, are limited to themodulation envelope and cannot easily distinguish precisely which RFcycle is associated with each data bit because the cycle-to-cycleamplitude differences are so small they are masked by link or systemnoise. Since the impulse radio waveform has no multi-cycle ambiguity,this allows positive determination of the waveform position to less thana wavelength—potentially, down to the noise floor of the system. Thistime position measurement can be used to measure propagation delay todetermine link distance, and once link distance is known, to transfer atime reference to an equivalently high degree of precision. Theinventors of the present invention have built systems that have shownthe potential for centimeter distance resolution, which is equivalent toabout 30 ps of time transfer resolution. See, for example, commonlyowned, co-pending applications Ser. No. 09/045,929, filed Mar. 23, 1998,titled “Ultrawide-Band Position Determination System and Method”, andSer. No. 09/083,993, filed May 26, 1998, titled “System and Method forDistance Measurement by Inphase and Quadrature Signals in a RadioSystem,” both of which are incorporated herein by reference.

In addition to the methods articulated above, impulse radio technologyalong with Time Division Multiple Access algorithms and Time Domainpacket radios can achieve geo-positioning capabilities in a radionetwork. This geo-positioning method allows ranging to occur within anetwork of radios without the necessity of a full duplex exchange amongevery pair of radios.

Exemplary Transceiver Implementation

Transmitter

An exemplary embodiment of an impulse radio transmitter 602 of animpulse radio communication system having one subcarrier channel willnow be described with reference to FIG. 6.

The transmitter 602 comprises a time base 604 that generates a periodictiming signal 606. The time base 604 typically comprises a voltagecontrolled oscillator (VCO), or the like, having a high timing accuracyand low jitter, on the order of picoseconds (ps). The voltage control toadjust the VCO center frequency is set at calibration to the desiredcenter frequency used to define the transmitter's nominal pulserepetition rate. The periodic timing signal 606 is supplied to aprecision timing generator 608.

The precision timing generator 608 supplies synchronizing signals 610 tothe code source 612 and utilizes the code source output 614 togetherwith an internally generated subcarrier signal (which is optional) andan information signal 616 to generate a modulated, coded timing signal618. The code source 612 comprises a storage device such as a randomaccess memory (RAM), read only memory (ROM), or the like, for storingsuitable codes and for outputting the PN codes as a code signal 614.Alternatively, maximum length shift registers or other computationalmeans can be used to generate the codes.

An information source 620 supplies the information signal 616 to theprecision timing generator 608. The information signal 616 can be anytype of intelligence, including digital bits representing voice, data,imagery, or the like, analog signals, or complex signals.

A pulse generator 622 uses the modulated, coded timing signal 618 as atrigger to generate output pulses. The output pulses are sent to atransmit antenna 624 via a transmission line 626 coupled thereto. Theoutput pulses are converted into propagating electromagnetic pulses bythe transmit antenna 624. In the present embodiment, the electromagneticpulses are called the emitted signal, and propagate to an impulse radioreceiver 702, such as shown in FIG. 7, through a propagation medium,such as air, in a radio frequency embodiment. In a preferred embodiment,the emitted signal is wide-band or ultrawide-band, approaching amonocycle pulse as in FIG. 1A. However, the emitted signal can bespectrally modified by filtering of the pulses. This bandpass filteringwill cause each monocycle pulse to have more zero crossings (morecycles) in the time domain. In this case, the impulse radio receiver canuse a similar waveform as the template signal in the cross correlatorfor efficient conversion.

Receiver

An exemplary embodiment of an impulse radio receiver (hereinafter calledthe receiver) for the impulse radio communication system is nowdescribed with reference to FIG. 7.

The receiver 702 comprises a receive antenna 704 for receiving apropagated impulse radio signal 706. A received signal 708 is input to across correlator or sampler 710 via a receiver transmission line,coupled to the receive antenna 704, and producing a baseband output 712.

The receiver 702 also includes a precision timing generator 714, whichreceives a periodic timing signal 716 from a receiver time base 718.This time base 718 is adjustable and controllable in time, frequency, orphase, as required by the lock loop in order to lock on the receivedsignal 708. The precision timing generator 714 provides synchronizingsignals 720 to the code source 722 and receives a code control signal724 from the code source 722. The precision timing generator 714utilizes the periodic timing signal 716 and code control signal 724 toproduce a coded timing signal 726. The template generator 728 istriggered by this coded timing signal 726 and produces a train oftemplate signal pulses 730 ideally having waveforms substantiallyequivalent to each pulse of the received signal 708. The code forreceiving a given signal is the same code utilized by the originatingtransmitter to generate the propagated signal. Thus, the timing of thetemplate pulse train matches the timing of the received signal pulsetrain, allowing the received signal 708 to be synchronously sampled inthe correlator 710. The correlator 710 ideally comprises a multiplierfollowed by a short term integrator to sum the multiplier product overthe pulse interval.

The output of the correlator 710 is coupled to a subcarrier demodulator732, which demodulates the subcarrier information signal from thesubcarrier. The purpose of the optional subcarrier process, when used,is to move the information signal away from DC (zero frequency) toimprove immunity to low frequency noise and offsets. The output of thesubcarrier demodulator is then filtered or integrated in the pulsesummation stage 734. A digital system embodiment is shown in FIG. 7. Inthis digital system, a sample and hold 736 samples the output 735 of thepulse summation stage 734 synchronously with the completion of thesummation of a digital bit or symbol. The output of sample and hold 736is then compared with a nominal zero (or reference) signal output in adetector stage 738 to determine an output signal 739 representing thedigital state of the output voltage of sample and hold 736.

The baseband signal 712 is also input to a lowpass filter 742 (alsoreferred to as lock loop filter 742). A control loop comprising thelowpass filter 742, time base 718, precision timing generator 714,template generator 728, and correlator 710 is used to generate an errorsignal 744. The error signal 744 provides adjustments to the adjustabletime base 718 to time position the periodic timing signal 726 inrelation to the position of the received signal 708.

In a transceiver embodiment, substantial economy can be achieved bysharing part or all of several of the functions of the transmitter 602and receiver 702. Some of these include the time base 718, precisiontiming generator 714, code source 722, antenna 704, and the like.

FIGS. 8A-8C illustrate the cross correlation process and the correlationfunction. FIG. 8A shows the waveform of a template signal. FIG. 8B showsthe waveform of a received impulse radio signal at a set of severalpossible time offsets. FIG. 8C represents the output of the correlator(multiplier and short time integrator) for each of the time offsets ofFIG. 8B. Thus, this graph does not show a waveform that is a function oftime, but rather a function of time-offset. For any given pulsereceived, there is only one corresponding point that is applicable onthis graph. This is the point corresponding to the time offset of thetemplate signal used to receive that pulse. Further examples and detailsof precision timing can be found described in U.S. Pat. No. 5,677,927,and commonly owned co-pending application Ser. No. 09/146,524, filedSep. 3, 1998, titled “Precision Timing Generator System and Method” bothof which are incorporated herein by reference.

Recent Advances in Impulse Radio Communication

Modulation Techniques

To improve the placement and modulation of pulses and to find new andimproved ways that those pulses transmit information, various modulationtechniques have been developed. The modulation techniques articulatedabove as well as the recent modulation techniques invented andsummarized below are incorporated herein by reference.

FLIP Modulation

An impulse radio communications system can employ FLIP modulationtechniques to transmit and receive flip modulated impulse radio signals.Further, it can transmit and receive flip with shift modulated (alsoreferred to as quadrature flip time modulated (QFTM)) impulse radiosignals. Thus, FLIP modulation techniques can be used to create two,four, or more different data states.

Flip modulators include an impulse radio receiver with a time base, aprecision timing generator, a template generator, a delay, first andsecond correlators, a data detector and a time base adjustor. The timebase produces a periodic timing signal that is used by the precisiontiming generator to produce a timing trigger signal. The templategenerator uses the timing trigger signal to produce a template signal. Adelay receives the template signal and outputs a delayed templatesignal. When an impulse radio signal is received, the first correlatorcorrelates the received impulse radio signal with the template signal toproduce a first correlator output signal, and the second correlatorcorrelates the received impulse radio signal with the delayed templatesignal to produce a second correlator output signal. The data detectorproduces a data signal based on at least the first correlator outputsignal. The time base adjustor produces a time base adjustment signalbased on at least the second correlator output signal. The time baseadjustment signal is used to synchronize the time base with the receivedimpulse radio signal.

For greater elaboration of FLIP modulation techniques, the reader isdirected to the patent application entitled, “Apparatus, System andMethod for FLIP Modulation in an Impulse Radio Communication System”,Ser. No. 09/537,692, filed Mar. 29, 2000 and assigned to the assignee ofthe present invention. This patent application is incorporated herein byreference.

Vector Modulation

Vector Modulation is a modulation technique which includes the steps ofgenerating and transmitting a series of time-modulated pulses, eachpulse delayed by one of four pre-determined time delay periods andrepresentative of at least two data bits of information, and receivingand demodulating the series of time-modulated pulses to estimate thedata bits associated with each pulse. The apparatus includes an impulseradio transmitter and an impulse radio receiver.

The transmitter transmits the series of time-modulated pulses andincludes a transmitter time base, a time delay modulator, a code timemodulator, an output stage, and a transmitting antenna. The receiverreceives and demodulates the series of time-modulated pulses using areceiver time base and two correlators, one correlator designed tooperate after a pre-determined delay with respect to the othercorrelator. Each correlator includes an integrator and a comparator, andmay also include an averaging circuit that calculates an average outputfor each correlator, as well as a track and hold circuit for holding theoutput of the integrators. The receiver further includes an adjustabletime delay circuit that may be used to adjust the pre-determined delaybetween the correlators in order to improve detection of the series oftime-modulated pulses.

For greater elaboration of Vector modulation techniques, the reader isdirected to the patent application entitled, “Vector Modulation Systemand Method for Wideband Impulse Radio Communications”, Ser. No.09/169,765, filed Dec. 9, 1999 and assigned to the assignee of thepresent invention. This patent application is incorporated herein byreference.

Receivers

Because of the unique nature of impulse radio receivers severalmodifications have been recently made to enhance system capabilities.

Multiple Correlator Receivers

Multiple correlator receivers utilize multiple correlators thatprecisely measure the impulse response of a channel and whereinmeasurements can extend to the maximum communications range of a system,thus, not only capturing ultra-wideband propagation waveforms, but alsoinformation on data symbol statistics. Further, multiple correlatorsenable rake acquisition of pulses and thus faster acquisition, trackingimplementations to maintain lock and enable various modulation schemes.Once a tracking correlator is synchronized and locked to an incomingsignal, the scanning correlator can sample the received waveform atprecise time delays relative to the tracking point. By successivelyincreasing the time delay while sampling the waveform, a complete,time-calibrated picture of the waveform can be collected.

For greater elaboration of utilizing multiple correlator techniques, thereader is directed to the patent application entitled, “System andMethod of using Multiple Correlator Receivers in an Impulse RadioSystem”, Ser. No. 09/537,264, filed Mar. 29, 2000 and assigned to theassignee of the present invention. This patent application isincorporated herein by reference.

Fast Locking Mechanisms

Methods to improve the speed at which a receiver can acquire and lockonto an incoming impulse radio signal have been developed. In oneapproach, a receiver comprises an adjustable time base to output asliding periodic timing signal having an adjustable repetition rate anda decode timing modulator to output a decode signal in response to theperiodic timing signal. The impulse radio signal is cross-correlatedwith the decode signal to output a baseband signal. The receiverintegrates T samples of the baseband signal and a threshold detectoruses the integration results to detect channel coincidence. A receivercontroller stops sliding the time base when channel coincidence isdetected. A counter and extra count logic, coupled to the controller,are configured to increment or decrement the address counter by one ormore extra counts after each T pulses is reached in order to shift thecode modulo for proper phase alignment of the periodic timing signal andthe received impulse radio signal. This method is described in detail inU.S. Pat. No. 5,832,035 to Fullerton, incorporated herein by reference.

In another approach, a receiver obtains a template pulse train and areceived impulse radio signal. The receiver compares the template pulsetrain and the received impulse radio signal to obtain a comparisonresult. The system performs a threshold check on the comparison result.If the comparison result passes the threshold check, the system locks onthe received impulse radio signal. The system may also perform a quickcheck, a synchronization check, and/or a command check of the impulseradio signal. For greater elaboration of this approach, the reader isdirected to the patent application entitled, “Method and System for FastAcquisition of Ultra Wideband Signals”, Ser. No. 09/538,292, filed Mar.29, 2000 and assigned to the assignee of the present invention. Thispatent application is incorporated herein by reference.

Baseband Signal Converters

A receiver has been developed which includes a baseband signal converterdevice and combines multiple converter circuits and an RF amplifier in asingle integrated circuit package. Each converter circuit includes anintegrator circuit that integrates a portion of each RF pulse during asampling period triggered by a timing pulse generator. The integratorcapacitor is isolated by a pair of Schottky diodes connected to a pairof load resistors. A current equalizer circuit equalizes the currentflowing through the load resistors when the integrator is not sampling.Current steering logic transfers load current between the diodes and aconstant bias circuit depending on whether a sampling pulse is present.

For greater elaboration of utilizing baseband signal converters, thereader is directed to the patent application entitled, “Baseband SignalConverter for a Wideband Impulse Radio Receiver”, Ser. No. 09/356,384,filed Jul. 16, 1999 and assigned to the assignee of the presentinvention. This patent application is incorporated herein by reference.

Power Control and Interference

Power Control

Power control improvements have been invented with respect to impulseradios. The power control systems comprise a first transceiver thattransmits an impulse radio signal to a second transceiver. A powercontrol update is calculated according to a performance measurement ofthe signal received at the second transceiver. The transmitter power ofeither transceiver, depending on the particular embodiment, is adjustedaccording to the power control update. Various performance measurementsare employed according to the current invention to calculate a powercontrol update, including bit error rate, signal-to-noise ratio, andreceived signal strength, used alone or in combination. Interference isthereby reduced, which is particularly important where multiple impulseradios are operating in close proximity and their transmissionsinterfere with one another. Reducing the transmitter power of each radioto a level that produces satisfactory reception increases the totalnumber of radios that can operate in an area without saturation.Reducing transmitter power also increases transceiver efficiency.

For greater elaboration of utilizing baseband signal converters, thereader is directed to the patent application entitled, “System andMethod for Impulse Radio Power Control”, Ser. No. 09/332,501, filed Jun.14, 1999 and assigned to the assignee of the present invention. Thispatent application is incorporated herein by reference.

Mitigating Effects of Interference

To assist in mitigating interference to impulse radio systems amethodology has been invented. The method comprises the steps of: (a)conveying the message in packets; (b) repeating conveyance of selectedpackets to make up a repeat package; and (c) conveying the repeatpackage a plurality of times at a repeat period greater than twice theoccurrence period of the interference. The communication may convey amessage from a proximate transmitter to a distal receiver, and receive amessage by a proximate receiver from a distal transmitter. In such asystem, the method comprises the steps of: (a) providing interferenceindications by the distal receiver to the proximate transmitter; (b)using the interference indications to determine predicted noise periods;and (c) operating the proximate transmitter to convey the messageaccording to at least one of the following: (1) avoiding conveying themessage during noise periods; (2) conveying the message at a higherpower during noise periods; (3) increasing error detection coding in themessage during noise periods; (4) re-transmitting the message followingnoise periods; (5) avoiding conveying the message when interference isgreater than a first strength; (6) conveying the message at a higherpower when the interference is greater than a second strength; (7)increasing error detection coding in the message when the interferenceis greater than a third strength; and (8) re-transmitting a portion ofthe message after interference has subsided to less than a predeterminedstrength.

For greater elaboration of mitigating interference to impulse radiosystems, the reader is directed to the patent application entitled,“Method for Mitigating Effects of Interference in Impulse RadioCommunication”, Ser. No. 09/587,033, filed Jun. 2, 1999 and assigned tothe assignee of the present invention. This patent application isincorporated herein by reference.

Moderating Interference while Controlling Equipment

Yet another improvement to impulse radio includes moderatinginterference with impulse radio wireless control of an appliance; thecontrol is affected by a controller remote from the appliancetransmitting impulse radio digital control signals to the appliance. Thecontrol signals have a transmission power and a data rate. The methodcomprises the steps of: (a) in no particular order: (1) establishing amaximum acceptable noise value for a parameter relating to interferingsignals; (2) establishing a frequency range for measuring theinterfering signals; (b) measuring the parameter for the interferencesignals within the frequency range; and (c) when the parameter exceedsthe maximum acceptable noise value, effecting an alteration oftransmission of the control signals.

For greater elaboration of moderating interference while effectingimpulse radio wireless control of equipment, the reader is directed tothe patent application entitled, “Method and Apparatus for ModeratingInterference While Effecting Impulse Radio Wireless Control ofEquipment”, Ser. No. 09/586,163, filed Jun. 2, 1999 and assigned to theassignee of the present invention. This patent application isincorporated herein by reference.

Coding Advances

The improvements made in coding can directly improve the characteristicsof impulse radio as used in the present invention. Specialized codingtechniques may be employed to establish temporal and/or non-temporalpulse characteristics such that a pulse train will possess desirableproperties. Coding methods for specifying temporal and non-temporalpulse characteristics are described in commonly owned, co-pendingapplications entitled “A Method and Apparatus for Positioning Pulses inTime”, Ser. No. 09/592,249, and “A Method for Specifying Non-TemporalPulse Characteristics”, Ser. No. 09/592,250, both filed Jun. 12, 2000,and both of which are incorporated herein by reference. Essentially, atemporal or non-temporal pulse characteristic value layout is defined,an approach for mapping a code to the layout is specified, a code isgenerated using a numerical code generation technique, and the code ismapped to the defined layout per the specified mapping approach.

A temporal or non-temporal pulse characteristic value layout may befixed or non-fixed and may involve value ranges, discrete values, or acombination of value ranges and discrete values. A value range layoutspecifies a range of values for a pulse characteristic that is dividedinto components that are each subdivided into subcomponents, which canbe further subdivided, ad infinitum. In contrast, a discrete valuelayout involves uniformly or non-uniformly distributed discrete pulsecharacteristic values. A non-fixed layout (also referred to as a deltalayout) involves delta values relative to some reference value such asthe characteristic value of the preceding pulse. Fixed and non-fixedlayouts, and approaches for mapping code element values to them, aredescribed in co-owned, co-pending applications, entitled “Method forSpecifying Pulse Characteristics using Codes”, Ser. No. 09/592,290 and“A Method and Apparatus for Mapping Pulses to a Non-Fixed Layout”, Ser.No. 09/591,691, both filed on Jun. 12, 2000 and both of which areincorporated herein by reference.

A fixed or non-fixed characteristic value layout may include one or morenon-allowable regions within which a characteristic value of a pulse isnot allowed. A method for specifying non-allowable regions to preventcode elements from mapping to non-allowed characteristic values isdescribed in co-owned, co-pending application entitled “A Method forSpecifying Non-Allowable Pulse Characteristics”, Ser. No. 09/592,289,filed Jun. 12, 2000 and incorporated herein by reference. A relatedmethod that conditionally positions pulses depending on whether or notcode elements map to non-allowable regions is described in co-owned,co-pending application, entitled “A Method and Apparatus for PositioningPulses Using a Layout having Non-Allowable Regions”, Ser. No. 09/592,248and incorporated herein by reference.

Typically, a code consists of a number of code elements having integeror floating-point values. A code element value may specify a singlepulse characteristic (e.g., pulse position in time) or may be subdividedinto multiple components, each specifying a different pulsecharacteristic. For example, a code having seven code elements eachsubdivided into five components (c0-c4) could specify five differentcharacteristics of seven pulses. A method for subdividing code elementsinto components is described in commonly owned, co-pending applicationentitled “Method for Specifying Pulse Characteristics using Codes”, Ser.No. 09/592,290, filed Jun. 12, 2000 previously referenced and againincorporated herein by reference. Essentially, the value of each codeelement or code element component (if subdivided) maps to a value rangeor discrete value within the defined characteristic value layout. If avalue range layout is used an offset value is typically employed tospecify an exact value within the value range mapped to by the codeelement or code element component.

The signal of a coded pulse train can be generally expressed:${s_{tr}^{(k)}(t)} = {\sum\limits_{j}{\left( {- 1} \right)^{f_{j}^{(k)}}a_{j}^{(k)}{\omega \left( {{{c_{j}^{(k)}t} - T_{j}^{(k)}},b_{j}^{(k)}} \right)}}}$

where k is the index of a transmitter, j is the index of a pulse withinits pulse train, (−1)f_(j) ^((k)), a_(j) ^((k)), C_(j) ^((k)), and b_(j)^((k)) are the coded polarity, amplitude, width, and waveform of the jthpulse of the kth transmitter, and T_(j) ^((k)) is the coded time shiftof the jth pulse of the kth transmitter. Note: When a given non-temporalcharacteristic does not vary (i.e., remains constant for all pulses inthe pulse train), the corresponding code element component is removedfrom the above expression and the non-temporal characteristic valuebecomes a constant in front of the summation sign.

Various numerical code generation methods can be employed to producecodes having certain correlation and spectral properties. Such codestypically fall into one of two categories: designed codes andpseudorandom codes.

A designed code may be generated using a quadratic congruential,hyperbolic congruential, linear congruential, Costas array or other suchnumerical code generation technique designed to generate codesguaranteed to have certain correlation properties. Each of thesealternative code generation techniques has certain characteristics to beconsidered in relation to the application of the pulse transmissionsystem employing the code. For example, Costas codes have nearly idealautocorrelation properties but somewhat less than idealcross-correlation properties, while linear congruential codes havenearly ideal cross-correlation properties but less than idealautocorrelation properties. In some cases, design tradeoffs may requirethat a compromise between two or more code generation techniques be madesuch that a code is generated using a combination of two or moretechniques. An example of such a compromise is an extended quadraticcongruential code generation approach that uses two ‘independent’operators, where the first operator is linear and the second operator isquadratic. Accordingly, one, two, or more code generation techniques orcombinations of such techniques can be employed to generate a codewithout departing from the scope of the invention.

A pseudorandom code may be generated using a computer's random numbergenerator, binary shift-register(s) mapped to binary words, a chaoticcode generation scheme, or another well-known technique. Such‘random-like’ codes are attractive for certain applications since theytend to spread spectral energy over multiple frequencies while having‘good enough’ correlation properties, whereas designed codes may havesuperior correlation properties but have spectral properties that maynot be as suitable for a given application.

Computer random number generator functions commonly employ the linearcongruential generation (LCG) method or the Additive Lagged-FibonacciGenerator (ALFG) method. Alternative methods include inversivecongruential generators, explicit-inversive congruential generators,multiple recursive generators, combined LCGs, chaotic code generators,and Optimal Golomb Ruler (OGR) code generators. Any of these or othersimilar methods can be used to generate a pseudorandom code withoutdeparting from the scope of the invention, as will be apparent to thoseskilled in the relevant art.

Detailed descriptions of code generation and mapping techniques areincluded in a co-owned patent application entitled “A Method andApparatus for Positioning Pulses in Time”, Ser. No. 09/638,150, filedAug. 15, 2000, which is hereby incorporated by reference.

It may be necessary to apply predefined criteria to determine whether agenerated code, code family, or a subset of a code is acceptable for usewith a given UWB application. Criteria to consider may includecorrelation properties, spectral properties, code length, non-allowableregions, number of code family members, or other pulse characteristics.A method for applying predefined criteria to codes is described inco-owned, co-pending application, entitled “A Method and Apparatus forSpecifying Pulse Characteristics using a Code that Satisfies PredefinedCriteria”, Ser. No. 09/592,288, filed Jun. 12, 2000 and is incorporatedherein by reference.

In some applications, it may be desirable to employ a combination of twoor more codes. Codes may be combined sequentially, nested, orsequentially nested, and code combinations may be repeated. Sequentialcode combinations typically involve transitioning from one code to thenext after the occurrence of some event. For example, a code withproperties beneficial to signal acquisition might be employed until asignal is acquired, at which time a different code with more idealchannelization properties might be used. Sequential code combinationsmay also be used to support multicast communications. Nested codecombinations may be employed to produce pulse trains having desirablecorrelation and spectral properties. For example, a designed code may beused to specify value range components within a layout and a nestedpseudorandom code may be used to randomly position pulses within thevalue range components. With this approach, correlation properties ofthe designed code are maintained since the pulse positions specified bythe nested code reside within the value range components specified bythe designed code, while the random positioning of the pulses within thecomponents results in desirable spectral properties. A method forapplying code combinations is described in co-owned, co-pendingapplication, entitled “A Method and Apparatus for Applying Codes HavingPre-Defined Properties”, Ser. No. 09/591,690, filed Jun. 12, 2000 whichis incorporated herein by reference.

Preferred Embodiments of the Present Invention

Referring to FIGS. 9-27, there are disclosed two preferred embodimentsof systems 900 and 900′, electronic monitors 910 and 910′ and methods1100 and 1500 in accordance with the present invention.

Although the present invention is described as using impulse radiotechnology, it should be understood that the present invention can beused with any type of ultra wideband technology, but is especiallysuited for use with time-modulated ultra wideband technology.Accordingly, the systems 900 and 900′, electronic monitors 910 and 910′and methods 1100 and 1500 should not be construed in a limited manner.

Referring to FIG. 9, there is a diagram illustrating the basiccomponents of a first embodiment of the system 900 in accordance withthe present invention. Essentially, the system 900 includes anelectronic monitor 910 attached to a person 920 that has been placedunder house arrest or otherwise confined to their home 930. Theelectronic monitor 910 can continually or periodically transmit animpulse radio signal 915 to a base unit 940. The base unit 940 can becoupled to or incorporated within a telephone 950 (e.g., land-basedphone or wireless phone).

If the base unit 940 fails to receive the impulse radio signal 915, thenthe base unit 940 interacts with the telephone phone 950 to send analarm signal 955 to a central station 960. In response to receiving thealarm signal 955, the central station 960 initiates a visual alarmand/or audio alarm to warn monitoring personnel 970 that the person 920is no longer located in the home 930 or within the receiving range ofthe base unit 940. The monitoring personnel 970 including, for example,police officers or parole officers can then attempt to locate the person920.

If the base unit 940 receives the impulse radio signal 915, then thebase unit 940 does not interact with the telephone 950 to send the alarmsignal 955 to the central station 960. Since there is no alarm signal955, the monitoring personnel 970 can safely assume that the person 920is still located in the home 930 or within the receiving range of thebase unit 940. Of course, the central station 960 can effectively tracka lot of people 920 located in different homes 930 and/or the same home930.

The impulse radio technology used to transmit and receive the impulseradio signal 915 within the present invention also helps to prevent thetriggering of false alarms that are so problematic with conventionalhouse arrest monitoring systems. Again, conventional house arrestmonitoring systems use standard radio technology that is susceptible to“dead zones” in the home. In particular, the closed structure of a homemakes it difficult for an electronic monitor (including a standard radiotransmitter coupled to a person) to maintain continuous radio contactwith a standard radio receiver as the person moves through the home. Assuch, the central station may receive an alarm that the electronicmonitor secured to the person is no longer communicating to the standardradio receiver even though the person is still in the home. Forinstance, the alarm may be triggered because the standard radio signalssent from the standard radio transmitter cannot penetrate a certain wallor floor within the home to reach the standard radio receiver. Thepresent invention helps reduce these types of false alarms because theimpulse radio signals 915 transmitted from the electronic monitor 910 tothe base unit 940 are located very close to DC which makes theattenuation due to walls and floors minimal compared to standard radiosignals.

In addition, conventional house arrest monitoring systems use standardradio technology that is susceptible to multipath interference which canbe very problematic in a closed structure such as a home. Again,multipath interference is an error caused by the interference of astandard radio signal that has reached a standard radio receiver by twoor more paths. Essentially, the standard radio receiver may not be ableto demodulate the standard radio signal because the transmitted radiosignal effectively cancels itself out by bouncing of walls and floorsbefore reaching the standard radio receiver. The present invention isnot affected by multipath interference because the impulses of theimpulse radio signal 915 arriving from delayed multipath reflectionstypically arrive outside a correlation (or demodulation) period of thebase unit 940. Therefore, impulse radio technology effectively enablesmonitoring personnel 970 to determine if a person 920 carrying anelectronic monitor 910 is still located in their home 930 in a mannernot possible with conventional house arrest monitoring systems.

Referring to FIG. 10, there is a diagram illustrated in greater detailthe electronic monitor 910 of the system 900 shown in FIG. 9. Theelectronic monitor 910 can be attached or secured to the person 920 withthe aid of a fastening mechanism 1002. The fastening mechanism 1002typically secures the electronic monitor 910 to an arm or leg of theperson 920. Alternatively, the fastening mechanism 1002 can secure theelectronic monitor 910 to any external part or internal part of theperson 920. Moreover, the electronic monitor 910 includes an impulseradio transmitter 602 (see FIG. 6) capable of transmitting apredetermined impulse radio signal 915 to the base unit 940 whichincludes an impulse radio receiver 702 (see FIG. 7). How the electronicmonitor 910 and the base unit 940 interact with one another usingimpulse radio signals can be better understood by referring to theaforementioned description.

Referring to FIG. 11, there is illustrated a flowchart of the basicsteps of a preferred method 1100 for tracking a person under housearrest in accordance with the first embodiment of the present invention.Beginning at step 1102, the electronic monitor 910 (including theimpulse radio transmitter 602) is attached to the person 920 with theaid of the fastening mechanism 1002. Again, the fastening mechanism 1002typically secures the electronic monitor 910 to an arm or leg of theperson 920. Alternatively, the fastening mechanism 1002 can secure theelectronic monitor 910 to any external part or internal part of theprisoner 920.

At step 1104, the electronic monitor 910 operates either continually orat times chosen by the monitoring personnel 970 to transmit the impulseradio signal 915 to the base unit 940. In particular, the electronicmonitor 910 operates to transmit an impulse radio signal 915 including atrain of modulated pulses that can be received and integrated by thebase unit 940 to verify that the person 920 is located in or near thehome 930 and has not removed or tampered with the electronic monitor910.

At step 1106, the base unit 940 operates to determine if the impulseradio signal 915 was received from the electronic monitor 910. If no,then at step 1108, the base unit 940 interacts with the telephone 950which, in turn, sends the alarm signal 955 to the central station 960.Upon receiving the alarm signal 955, the central station 960 at step1110 operates to initiate a visual alarm and/or audio alarm to warnmonitoring personnel 970 that the person 920 is no longer located in thehome 930 or within the receiving range of the base unit 940, or that theelectronic monitor 910 has been tampered with or removed.

If the base unit 940 fails to receive the impulse radio signal 915 atstep 1106, then the central station 960 at step 1112 does not need toalert the monitoring personnel 970. In this situation, the monitoringpersonnel 970 can safely assume that the person 920 is still carryingthe electronic monitor 910 and still located within or near the home930.

Referring to FIG. 12, there is a diagram illustrating the basiccomponents of a second embodiment of the system 900 in accordance withthe present invention. The second embodiment of the system 900 isillustrated using prime referenced numbers. Basically, the system 900′includes an electronic monitor 910′ attached to a person 920 that hasbeen placed under house arrest or otherwise confined to their home 930.The electronic monitor 910′ can transmit and receive impulse radiosignals 915 to and from a base unit 940′. Alternatively, the electronicmonitor 910′ can use a reference impulse radio unit 1202′ (only fourshown) to interact with the base unit 940′. The base unit 940′ can becoupled to or incorporated within a telephone 950 (e.g., land-based orwireless phone). The telephone 950 transmits and receives signals 955′to and from the central station 960′. The central station 960′ iscapable of displaying information contained in the signals 955′ tomonitoring personnel 970.

For instance, the information contained in the signals 955′ can indicatethe current position of the person 920 in the home 930′ and/or indicatethe vital sign(s) of the person 920. In addition, the electronic monitor910′ and the central station 960′ can be used to enable communicationsbetween the person 920 and the monitoring personnel 970. As will bedescribed in greater detail below, the electronic monitor 910′,reference impulse radio units 1202″ and base unit 940′ utilize therevolutionary position capabilities and communication capabilities ofimpulse radio technology to track and/or monitor a person in a mannernot possible with conventional house arrest monitoring systems.

The central station 960′ includes a display 1204′ containing an overlayof the layout of the home 930′. The reference impulse radio units 1202″(only 4 shown) have known positions and are located to provide maximumcoverage throughout and outside the home 930. The base unit 940′ has awireless connection or hardwire connection to the reference impulseradio units 1202″, and the electronic monitor 910′ has a wirelessconnection to the reference impulse radio units. Again, the electronicmonitor 910′ is capable of interacting with one or more of the referenceimpulse radio units 1202′ such that either the electronic monitor 910′,the base unit 940′, or one of the reference impulse radio units 1202′ isable to calculate at any given time the current position of the person920 within the home 930′. A variety of impulse radio positioningnetworks (e.g., reference impulse radio units 1202′, base unit 940′ andelectronic monitor 910′) that enable the present invention to performthe positioning and tracking functions are described in greater detailbelow with respect to FIGS. 16-27.

Moreover, the central station 960′ can be programmed to track only thepeople 920 that the monitoring personnel 970 want to watch at one time.The central station 960′ can also be programmed to sound an alarm forthe monitoring personnel 970 whenever a person 920 roams near the end ofthe range of the reference impulse radio units 1202′ or the base unit940′. The central station 960′ can also cause the electronic monitor910′ to sound an alarm for the person 920 whenever a person 920 roamsnear the end of or outside the range of the reference impulse radiounits 1202′ or the base unit 940′. Also, the central station 960′ can beprogrammed to sound an alarm whenever the electronic monitor 910′ istampered with or removed from the person 920.

It should be understood that the impulse radio technology incorporatedwithin the reference impulse radio units 1202′ also enables an impulseradar operation. This radar operation allows a reference impulse radiounit 1202′ to sense the movement of a person that is not carrying anelectronic monitor 910′. Of course, the central station 960′ is not beable to identify and track a person not carrying an electronic monitor910′ but is able to determine how many people are in the home 930.

It should also be understood that the monitoring personnel 970 cancontrol when and for how long the electronic monitor 910′ is in anoperating state. Thus, the monitoring personnel 970 can help increasethe amount of time that the electronic monitor 910′ can operate beforeneeding a recharge or a new battery.

Referring to FIG. 13, there is a diagram illustrating in greater detailthe electronic monitor 910′ of the system 900′ shown in FIG. 12. Theelectronic monitor 910′ can be attached or secured to the person 920with the aid of a fastening mechanism 1002′. The fastening mechanism1002 typically secures the electronic monitor 910′ to an arm or leg ofthe person 920. Alternatively, the fastening mechanism 1002′ can securethe electronic monitor 910′ to any external part or internal part of theperson 920.

The electronic monitor 910′ includes an impulse radio transmitter 602′and an impulse radio receiver 702′ (see FIGS. 6 and 7). The impulseradio transmitter 602′ and impulse radio receiver 702′ collectivelyknown as an impulse radio unit 1302′ are capable of interacting with oneor more reference impulse radio units 1202′ such that either theelectronic monitor 910′, the base unit 940′ or one of the referenceimpulse radio units 1202′ can calculate the current position of theperson 920 within or around the home 930. How the electronic monitor910′, base unit 940′ and reference impulse radio units 1202′ interactwith one another using impulse radio signals to determine the currentposition of the person 920 can be better understood by referring to thedescription associated with FIGS. 16-27.

For instance, the positioning and tracking functions can be accomplishedby stepping through several steps. The first step is for the referenceimpulse radio units 1202′ to synchronize together and begin passinginformation. Then, when an electronic monitor 910′ is powered on, itsynchronizes itself to the previously synchronized reference impulseradio units 1202′. Once the electronic monitor 910′ is synchronized, itbegins collecting and time-tagging range measurements from any availablereference impulse radio units 1202′. The electronic monitor 910′ thentakes these time-tagged ranges and, using a least squares-based orsimilar estimator, calculates its position within or near the home 930.Finally, the electronic monitor 910′ forwards its position calculationto the base unit 940′ and then the central station 960′ for storage andreal-time display. Alternatively, one of the reference impulse radiounits 1202′ can calculate the position of the electronic monitor 910′.

The electronic monitor 910′ may also include a sensor 1304′ operable tomonitor at least one vital sign of the person 920. For instance, thesensor 1304′ is capable of functioning as a breath (alcohol) monitor,heart rate monitor, blood pressure monitor, blood monitor and/orperspiration monitor. The sensor 1304′ can monitor one or more vitalsigns of the person 920 and forward that information to the impulseradio transmitter 602 which, in turn, modulates and forwards theinformation using impulse radio signals 915′ to the base unit 940′.Thereafter, the base unit 940′ by way of the telephone 950′ forwards theinformation to the central station 960′. The sensor 1304′ can have ahardwire connection or wireless connection (when located away from theelectronic monitor 910′) to the impulse radio transmitter 602. It shouldbe understood that the electronic monitor 910 of the first embodimentcan be adapted to include a sensor 1304′.

The central station 960′ (see FIG. 12) can be programmed to sound analarm for the monitoring personnel 970 whenever a monitored vital signfalls outside a predetermined range of acceptable conditions. Inaddition, the central station 960′ can cause the electronic monitor 910′to sound an alarm for the person 920 whenever a monitored vital signfalls outside a predetermined range of acceptable conditions.

Alternatively, the central station 960′ can remotely activate the sensor1304′ to monitor any one of the vital signs of the person 920. Thesensor 1304′ can also be designed to compare a monitored vital sign to apredetermined range of acceptable conditions. In the event, the sensor1304′ monitors a vital sign that falls outside of a predetermined rangeof acceptable conditions, then the electronic monitor 910′ can send analert to the central station 960′. A variety of monitoring techniquesthat can be used in the present invention have been disclosed in U.S.patent application Ser. No. 09/407,106, which has been incorporated intothe present application.

The electronic monitor 910′ may also include an interface unit 1306′(e.g., speaker, microphone) which enables two-way communications betweenthe person 920 and monitoring personnel 970. As such, the monitoringpersonnel 970 may use the interface unit 1304′ to eavesdrop on theperson 920 or to inform the person that a rule has been violated. Ofcourse, the person 920 may not be aware when there is or is not aconnection between the electronic monitor 910′ and the central station960′. And, if the connection between the electronic monitor 910′ and thecentral station 960′ was broken for any reason the central station 960′could alert the monitoring personnel 970. The monitoring personnel 970can also use the interface unit 1306′ to verify the identity of theperson 920 by using voice recognition technology.

Referring to FIG. 14, there is a diagram illustrating a GPS based optionand work place option that can be incorporated within the system 900′ ofFIG. 12. To utilize the GPS option, the electronic monitor 910′incorporates a GPS receiver 1402′ (see FIG. 13) capable of interactingwith GPS satellites 1404′ to determine the current position of theperson 920 when he or she is located outside the home 930′. Theelectronic monitor 910′ can also include a wireless radio unit 1406′(see FIG. 13) used to inform the central station 960′ as to the currentlocation of the person 920. In addition, the wireless radio unit 1406′can enable the monitoring personnel 970 to communicate with and monitorthe person 920. To utilize the work place option, the building 932′ inwhich the person 920 works would have to be wired for impulse radiocommunications and impulse radio positioning in a similar manner as thehome 930′.

Referring to FIG. 15, there is a flowchart illustrating the basic stepsof a preferred method 1500 for tracking and monitoring a person underhouse arrest in accordance with the second embodiment of the presentinvention. Beginning at step 1502, the electronic monitor 910′ isattached to the person 920 with the aid of the fastening mechanism 1002.The fastening mechanism 1002 typically secures the electronic monitor910′ to an arm or leg of the person 920. Alternatively, the fasteningmechanism 1002 can secure the electronic monitor 910′ to any externalpart or internal part of the person 920.

At step 1504, the sensor 1304′ is coupled to the electronic monitor 910′in a manner so as to enable the monitoring of at least one vital sign ofthe person 920. As described above, the sensor 1304′ is capable offunctioning as a breath (alcohol) monitor, heart rate monitor, bloodpressure monitor, blood monitor and/or a perspiration monitor. Forinstance, the central station 960′ can monitor one or more vital signsof the person 920 to detect agitated states of the person 920 and/or thepresence of intoxicating substances (e.g., drugs and alcohol) within theperson 920. Moreover, the central station 960′ can compare the monitoredvital signs to a set of allowed activities and sound an alarm if thereare any variations from these allowed activities.

At step 1506, the electronic monitor 910′ can determine the location ofa person 920 within the home 930′ by interacting with a predeterminednumber of reference impulse radio units 1202′. After completing steps1504 and 1506, the electronic monitor 910′ operates to forward themonitored vital signs and/or the determined position of the person 920to the base unit 940′ and then to the central station 960′. It should benoted that the base unit 940′ or anyone of the reference impulse radiounits 1202′ is capable of determining the position of the electronicmonitor 910′.

At step 1508, the central station 960′ is operable to display an alarmwhenever the person 920 has abnormal vital sign(s), or roams outside therange of the reference impulse radio units 1202′ or intermediate unit940′ (for example) Also, the central station 960′ and/or electronicmonitor 910′ can be programmed to sound an alarm whenever the electronicmonitor 910′ is tampered with or removed from the person 920.

At step 1510, the central station 960′ and electronic monitor 910′ maybe used to establish communications between the person 920 andmonitoring personnel 970. For example, the monitoring personnel 970 mayuse the electronic monitor 910′ to eavesdrop on the person 920 or toinform the person that a rule has been violated. Moreover, themonitoring personnel 970 can use the communication capabilities of theelectronic monitor 910′ to verify the identity of the person 920.

At step 1512 (optional), the central station 960′ is capable of trackingthe position of the person 920 when he or she is located outside thehome 930′. The central station 960′ is able to track the position of theperson 920 located outside of the home 930′ by using GPS basedtechnology.

At step 1514 (optional), the central station 960′ is also capable oftracking the position and/or monitoring the vital signs of the person920 while they are at work. To accomplish this, the area in which theperson 920 works would have to be wired for impulse radio communicationsand impulse radio positioning in the same way as the home 930′.

Impulse Radio Positioning Networks in the Home Confinement Field

A variety of impulse radio positioning networks capable of performingthe positioning and tracking functions of the present invention aredescribed in this Section (see also U.S. patent application Ser. No.09/456,409). An impulse radio positioning network includes a set ofreference impulse radio units 1202′ (shown below as reference impulseradio units R1-R6), one or more electronic monitors 910′ (shown below aselectronic monitors M1-M3) and a central station 960′.

Synchronized Transceiver Tracking Architecture

Referring to FIG. 16, there is illustrated a block diagram of an impulseradio positioning network 1600 utilizing a synchronized transceivertracking architecture. This architecture is perhaps the most generic ofthe impulse radio positioning networks since both electronic monitors M1and M2 and reference impulse radio units R1-R4 are full two-waytransceivers. The network 1600 is designed to be scalable, allowing fromvery few electronic monitors M1 and M2 and reference impulse radio unitsR1-R4 to a very large number.

This particular example of the synchronized transceiver trackingarchitecture shows a network 1600 of four reference impulse radio unitsR1-R4 and two electronic monitors M1 and M2. The arrows between theradios represent two-way data and/or voice links. A fullyinter-connected network would have every radio continually communicatingwith every other radio, but this is not required and can be dependentupon the needs of the particular application.

Each radio is a two-way transceiver; thus each link between radios istwo-way (duplex). Precise ranging information (the distance between tworadios) is distributed around the network 1600 in such a way as to allowthe electronic monitors M1 and M2 to determine their precisethree-dimensional position within a local coordinate system. Thisposition, along with other data or voice traffic, can then be relayedfrom the electronic monitors M1 and M2 back to the reference masterimpulse radio unit R1, one of the other reference relay impulse radiounits R2-R4 or the central station 960′.

The radios used in this architecture are impulse radio two-waytransceivers. The hardware of the reference impulse radio units R1-R4and electronic monitors M1 and M2 is essentially the same. The firmware,however, varies slightly based on the functions each radio must perform.For example, the reference master impulse radio unit R1 directs thepassing of information and is typically responsible for collecting allthe data for external graphical display at the central station 960′. Theremaining reference relay impulse radio units R2-R4 contain a separateversion of the firmware, the primary difference being the differentparameters or information that each reference relay impulse radio unitR2-R4 must provide the network. Finally, the electronic monitors M1 andM2 have their own firmware version that calculates their position.

In FIG. 16, each radio link is a two-way link that allows for thepassing of information, both data and/or voice. The data-rates betweeneach radio link is a function of several variables including the numberof pulses integrated to get a single bit, the number of bits per dataparameter, the length of any headers required in the messages, the rangebin size, and the number of radios in the network.

By transmitting in assigned time slots and by carefully listening to theother radios transmit in their assigned transmit time slots, the entiregroup of radios within the network, both electronic monitors M1 and M2and reference impulse radio units R1-R4, are able to synchronizethemselves. The oscillators used on the impulse radio boards driftslowly in time, thus they may require continual monitoring andadjustment of synchronization. The accuracy of this synchronizationprocess (timing) is dependent upon several factors including, forexample, how often and how long each radio transmits.

The purpose of this impulse radio positioning network 1600 is to enablethe tracking of the electronic monitors M1 and M2. Tracking isaccomplished by stepping through several well-defined steps. The firststep is for the reference impulse radio units R1-R4 to synchronizetogether and begin passing information. Then, when a electronic monitorM1 or M2 enters the network area, it synchronizes itself to thepreviously synchronized reference impulse radio units R1-R4. Once theelectronic monitor M1 or M2 is synchronized, it begins collecting andtime-tagging range measurements from any available reference impulseradio units R1-R4 (or other electronic monitor M1 or M2). The electronicmonitor M1 or M2 then takes these time-tagged ranges and, using a leastsquares-based or similar estimator, calculates the position of theelectronic monitor M1 or M2 in local coordinates. If the situationwarrants and the conversion possible, the local coordinates can beconverted to any one of the worldwide coordinates such as Earth CenteredInertial (ECI), Earth Centered Earth Fixed (ECEF), or J2000 (inertialcoordinates fixed to year 2000). Finally, the electronic monitor M1 orM2 forwards its position calculation to the central station 960′ forstorage and real-time display.

Unsynchronized Transceiver Tracking Architecture

Referring to FIG. 17, there is illustrated a block diagram of an impulseradio positioning network 1700 utilizing an unsynchronized transceivertracking architecture. This architecture is similar to synchronizedtransceiver tracking of FIG. 16, except that the reference impulse radiounits R1-R4 are not time-synchronized. Both the electronic monitors M1and M2 and reference impulse radio units R1-R4 for this architecture arefull two-way transceivers. The network is designed to be scalable,allowing from very few electronic monitors M1 and M2 and referenceimpulse radio units R1-R4 and to a very large number.

This particular example of the unsynchronized transceiver trackingarchitecture shows a network 1700 of four reference impulse radio unitsR1-R4 and two electronic monitors M1 and M2. The arrows between theradios represent two-way data and/or voice links. A fullyinter-connected network would have every radio continually communicatingwith every other radio, but this is not required and can be defined asto the needs of the particular application.

Each radio is a two-way transceiver; thus each link between radios istwo-way (duplex). Precise ranging information (the distance between tworadios) is distributed around the network in such a way as to allow theelectronic monitors M1 and M2 to determine their precisethree-dimensional position within a local coordinate system. Thisposition, along with other data or voice traffic, can then be relayedfrom the electronic monitors M1 and M2 back to the reference masterimpulse radio unit R1, one of the other reference relay impulse radiounits R2-R3 or the central station 9601.

The radios used in the architecture of FIG. 17 are impulse radio two-waytransceivers. The hardware of the reference impulse radio units R1-R4and electronic monitors M1 and M2 is essentially the same. The firmware,however, varies slightly based on the functions each radio must perform.For example, the reference master impulse radio unit R1 directs thepassing of information, and typically is responsible for collecting allthe data for external graphical display at the central station 960′. Theremaining reference relay impulse radio units R2-R4 contain a separateversion of the firmware, the primary difference being the differentparameters or information that each reference relay radio must providethe network. Finally, the electronic monitors M1 and M2 have their ownfirmware version that calculates their position and displays it locallyif desired.

In FIG. 17, each radio link is a two-way link that allows for thepassing of information, data and/or voice. The data-rates between eachradio link is a function of several variables including the number ofpulses integrated to get a single bit, the number of bits per dataparameter, the length of any headers required in the messages, the rangebin size, and the number of radios in the network.

Unlike the radios in the synchronized transceiver tracking architecture,the reference impulse radio units R1-R4 in this architecture are nottime-synchronized as a network. These reference impulse radio unitsR1-R4 operate independently (free-running) and provide ranges to theelectronic monitors M1 and M2 either periodically, randomly, or whentasked. Depending upon the application and situation, the referenceimpulse radio units R1-R4 may or may not talk to other reference radiosin the network.

As with the architecture of FIG. 16, the purpose of this impulse radiopositioning network 1700 is to enable the tracking of electronicmonitors M1 and M2. Tracking is accomplished by stepping through severalsteps. These steps are dependent upon the way in which the referenceimpulse radio units R1-R4 range with the electronic monitors M1 and M2(periodically, randomly, or when tasked). When a electronic monitor M1or M2 enters the network area, it either listens for reference impulseradio units R1-R4 to broadcast, then responds, or it queries (tasks) thedesired reference impulse radio units R1-R4 to respond. The electronicmonitor M1 or M2 begins collecting and time-tagging range measurementsfrom reference (or other mobile) radios. The electronic monitor M1 or M2then takes these time-tagged ranges and, using a least squares-based orsimilar estimator, calculates the position of the electronic monitor M1or M2 in local coordinates. If the situation warrants and the conversionpossible, the local coordinates can be converted to any one of theworldwide coordinates such as Earth Centered Inertial (ECI), EarthCentered Earth Fixed (ECEF), or J2000 (inertial coordinates fixed toyear 2000). Finally, the electronic monitor M1 or M2 forwards itsposition calculation to the central station 960′ for storage andreal-time display.

Synchronized Transmitter Tracking Architecture

Referring to FIG. 18, there is illustrated a block diagram of an impulseradio positioning network 1800 utilizing a synchronized transmittertracking architecture. This architecture is perhaps the simplest of theimpulse radio positioning architectures, from the point-of-view of theelectronic monitors M1 and M2, since the electronic monitors M1 and M2simply transmit in a free-running sense. The network is designed to bescalable, allowing from very few electronic monitors M1 and M2 andreference impulse radio units R1-R4 to a very large number. Thisarchitecture is especially applicable to an “RF tag” (radio frequencytag) type of application.

This particular example of synchronized transmitter trackingarchitecture shows a network 1800 of four reference impulse radio unitsradios R1-R4 and two electronic monitors M1 and M2. The arrows betweenthe radios represent two-way and one-way data and/or voice links. Noticethat the electronic monitors M1 and M2 only transmit, thus they do notreceive the transmissions from the other radios.

Each reference impulse radio unit R1-R4 is a two-way transceiver; thuseach link between reference impulse radio units R1-R4 is two-way(duplex). Precise ranging information (the distance between two radios)is distributed around the network in such a way as to allow thesynchronized reference impulse radio units R1-R4 to receivetransmissions from the electronic monitors M1 and M2 and then determinethe three-dimensional position of the electronic monitors M1 and M2.This position, along with other data or voice traffic, can then berelayed from reference relay impulse radio units R2-R4 back to thereference master impulse radio unit R1 or the central station 960′.

The reference impulse radio units R1-R4 used in this architecture areimpulse radio two-way transceivers, the electronic monitors M1 and M2are one-way transmitters. The firmware in the radios varies slightlybased on the functions each radio must perform. For example, thereference master impulse radio unit R1 is designated to direct thepassing of information, and typically is responsible for collecting allthe data for external graphical display at the central station 960′. Theremaining reference relay impulse radio units R2-R4 contain a separateversion of the firmware, the primary difference being the differentparameters or information that each reference relay impulse radio unitR2-R4 must provide the network. Finally, the electronic monitors M1 andM2 have their own firmware version that transmits pulses inpredetermined sequences.

Each reference radio link is a two-way link that allows for the passingof information, data and/or voice. The data-rates between each radiolink is a function of several variables including the number of pulsesintegrated to get a single bit, the number of bits per data parameter,the length of any headers required in the messages, the range bin size,and the number of radios in the network.

By transmitting in assigned time slots and by carefully listening to theother radios transmit in their assigned transmit time slots, the entiregroup of reference impulse radio units R1-R4 within the network are ableto synchronize themselves. The oscillators used on the impulse radioboards drift slowly in time, thus they may require monitoring andadjustment to maintain synchronization. The accuracy of thissynchronization process (timing) is dependent upon several factorsincluding, for example, how often and how long each radio transmitsalong with other factors. The electronic monitors M1 and M2, since theyare transmit-only transmitters, are not time-synchronized to thesynchronized reference impulse radio units R1-R4.

The purpose of the impulse radio positioning network is to enable thetracking of electronic monitors M1 and M2. Tracking is accomplished bystepping through several well-defined steps. The first step is for thereference impulse radio units R1-R4 to synchronize together and beginpassing information. Then, when a electronic monitor M1 or M2 enters thenetwork area and begins to transmit pulses, the reference impulse radiounits R1-R4 pick up these pulses as time-of-arrivals (TOAs). MultipleTOAs collected by different synchronized reference impulse radio unitsR1-R4 are then converted to ranges, which are then used to calculate theXYZ position of the electronic monitor M1 or M2 in local coordinates. Ifthe situation warrants and the conversion possible, the localcoordinates can be converted to any one of the worldwide coordinatessuch as Earth Centered Inertial (ECI), Earth Centered Earth Fixed(ECEF), or J2000 (inertial coordinates fixed to year 2000). Finally, thereference impulse radio units R1-R4 forwards their position calculationto the central station 960′ for storage and real-time display.

Unsynchronized Transmitter Tracking Architecture

Referring to FIG. 19, there is illustrated a block diagram of an impulseradio positioning network 1900 utilizing an unsynchronized transmittertracking architecture. This architecture is very similar to thesynchronized transmitter tracking architecture except that the referenceimpulse radio units R1-R4 are not synchronized in time. In other words,both the reference impulse radio units R1-R4 and the electronic monitorsM1 and M2 are free-running. The network is designed to be scalable,allowing from very few electronic monitors M1 and M2 and referenceimpulse radio units R1-R4 to a very large number. This architecture isespecially applicable to an “RF tag” (radio frequency tag) type ofapplication.

This particular example of the unsynchronized transmitter trackingarchitecture shows a network 1900 of four reference impulse radio unitsR1-R4 and two electronic monitors M1 and M2. The arrows between theradios represent two-way and one-way data and/or voice links. Noticethat the electronic monitors M1 and M2 only transmit, thus they do notreceive the transmissions from the other radios. Unlike the synchronoustransmitter tracking architecture, the reference impulse radio unitsR1-R4 in this architecture are free-running (unsynchronized). There areseveral ways to implement this design, the most common involves relayingthe time-of-arrival (TOA) pulses from the electronic monitors M1 and M2and reference impulse radio units R1-R4, as received at the referenceimpulse radio units R1-R4, back to the reference master impulse radiounit R1 which communicates with the central station 960′.

Each reference impulse radio unit R1-R4 in this architecture is atwo-way impulse radio transceiver; thus each link between referenceimpulse radio unit R1-R4 can be either two-way (duplex) or one-way(simplex). TOA information is typically transmitted from the referenceimpulse radio units R1-R4 back to the reference master impulse radiounit R1 where the TOAs are converted to ranges and then an XYZ positionof the electronic monitor M1 or M2, which can then be forwarded anddisplayed at the central station 960′.

The reference impulse radio units R1-R4 used in this architecture areimpulse radio two-way transceivers, the electronic monitors M1 and M2are one-way impulse radio transmitters. The firmware in the radiosvaries slightly based on the functions each radio must perform. Forexample, the reference master impulse radio R1 collects the TOAinformation, and is typically responsible for forwarding this trackingdata to the central station 960′. The remaining reference relay impulseradio units R2-R4 contain a separate version of the firmware, theprimary difference being the different parameters or information thateach reference relay impulse radio units R2-R4 must provide the network.Finally, the electronic monitors M1 and M2 have their own firmwareversion that transmits pulses in predetermined sequences.

Each reference radio link is a two-way link that allows for the passingof information, data and/or voice. The data-rates between each radiolink is a function of several variables including the number of pulsesintegrated to get a single bit, the number of bits per data parameter,the length of any headers required in the messages, the range bin size,and the number of radios in the network.

Since the reference impulse radio units R1-R4 and electronic monitors M1and M2 are free-running, synchronization is actually done by thereference master impulse radio unit R1. The oscillators used in theimpulse radios drift slowly in time, thus they may require monitoringand adjustment to maintain synchronization at the reference masterimpulse radio unit R1. The accuracy of this synchronization (timing) isdependent upon several factors including, for example, how often and howlong each radio transmits along with other factors.

The purpose of the impulse radio positioning network is to enable thetracking of electronic monitors M1 and M2. Tracking is accomplished bystepping through several steps. The most likely method is to have eachreference impulse radio unit R1-R4 periodically (randomly) transmit apulse sequence. Then, when a electronic monitor M1 or M2 enters thenetwork area and begins to transmit pulses, the reference impulse radiounits R1-R4 pick up these pulses as time-of-arrivals (TOAs) as well asthe pulses (TOAs) transmitted by the other reference radios. TOAs canthen either be relayed back to the reference master impulse radio unitR1 or just collected directly (assuming it can pick up all thetransmissions). The reference master impulse radio unit R1 then convertsthese TOAs to ranges, which are then used to calculate the XYZ positionof the electronic monitor M1 or M2. If the situation warrants and theconversion possible, the XYZ position can be converted to any one of theworldwide coordinates such as Earth Centered Inertial (ECI), EarthCentered Earth Fixed (ECEF), or J2000 (inertial coordinates fixed toyear 2000). Finally, the reference master impulse radio unit R1 forwardsits position calculation to the central station 960′ for storage andreal-time display.

Synchronized Receiver Tracking Architecture

Referring to FIG. 20, there is illustrated a block diagram of an impulseradio positioning network 2000 utilizing a synchronized receivertracking architecture. This architecture is different from thesynchronized transmitter tracking architecture in that in this designthe electronic monitors M1 and M2 determine their positions but are notable to broadcast it to anyone since they are receive-only radios. Thenetwork is designed to be scalable, allowing from very few electronicmonitors M1 and M2 and reference impulse radio units R1-R4 to a verylarge number.

This particular example of the synchronized receiver trackingarchitecture shows a network 2000 of four reference impulse radio unitsR1-R4 and two electronic monitors M1 and M2. The arrows between theradios represent two-way and one-way data and/or voice links. Noticethat the electronic monitors M1 and M2 receive transmissions from otherradios, and do not transmit.

Each reference impulse radio unit R1-R4 is a two-way transceiver, andeach electronic monitor M1 and M2 is a receive-only radio. Precise,synchronized pulses are transmitted by the reference network andreceived by the reference impulse radio units R1-R4 and the electronicmonitors M1 and M2. The electronic monitors M1 and M2 take thesetimes-of-arrival (TOA) pulses, convert them to ranges, then determinetheir XYZ positions. Since the electronic monitors M1 and M2 do nottransmit, only they themselves know their XYZ positions.

The reference impulse radio units R1-R4 used in this architecture areimpulse radio two-way transceivers, the electronic monitors M1 and M2are receive-only radios. The firmware for the radios varies slightlybased on the functions each radio must perform. For example, thereference master impulse radio unit R1 is designated to direct thesynchronization of the reference radio network. The remaining referencerelay impulse radio units R2-R4 contain a separate version of thefirmware, the primary difference being the different parameters orinformation that each reference relay impulse radio unit R2-R4 mustprovide the network. Finally, the electronic monitors M1 and M2 havetheir own firmware version that calculates their position and displaysit locally if desired.

Each reference radio link is a two-way link that allows for the passingof information, data and/or voice. The electronic monitors M1 and M2 arereceive-only. The data-rates between each radio link is a function ofseveral variables including the number of pulses integrated to get asingle bit, the number of bits per data parameter, the length of anyheaders required in the messages, the range bin size, and the number ofradios in the network.

By transmitting in assigned time slots and by carefully listening to theother reference impulse radio units R1-R4 transmit in their assignedtransmit time slots, the entire group of reference impulse radio unitsR1-R4 within the network are able to synchronize themselves. Theoscillators used on the impulse radio boards may drift slowly in time,thus they may require monitoring and adjustment to maintainsynchronization. The accuracy of this synchronization (timing) isdependent upon several factors including, for example, how often and howlong each radio transmits along with other factors.

The purpose of the impulse radio positioning network is to enable thetracking of electronic monitors M1 and M2. Tracking is accomplished bystepping through several well-defined steps. The first step is for thereference impulse radio units R1-R4 to synchronize together and beginpassing information. Then, when an electronic monitor M1 or M2 entersthe network area, it begins receiving the time-of-arrival (TOA) pulsesfrom the reference radio network. These TOA pulses are converted toranges, then the ranges are used to determine the XYZ position of theelectronic monitor M1 or M2 in local coordinates using a leastsquares-based estimator. If the situation warrants and the conversionpossible, the local coordinates can be converted to any one of theworldwide coordinates such as Earth Centered Inertial (ECI), EarthCentered Earth Fixed (ECEF), or J2000 (inertial coordinates fixed toyear 2000).

Unsynchronized Receiver Tracking Architecture

Referring to FIG. 21, there is illustrated a block diagram of an impulseradio positioning network 2100 utilizing an unsynchronized receivertracking architecture. This architecture is different from thesynchronized receiver tracking architecture in that in this design thereference impulse radio units R1-R4 are not time-synchronized. Similarto the synchronized receiver tracking architecture, electronic monitorsM1 and M2 determine their positions but cannot broadcast them to anyonesince they are receive-only radios. The network is designed to bescalable, allowing from very few electronic monitors M1 and M2 andreference impulse radio units R1-R4 to a very large number.

This particular example of the unsynchronized receiver trackingarchitecture shows a network 2100 of four reference impulse radio unitsR1-R4 and two electronic monitors M1 and M2. The arrows between theradios represent two-way and one-way data and/or voice links. Noticethat the electronic monitors M1 and M2 only receive transmissions fromother radios, and do not transmit.

Each reference impulse radio unit R1-R4 is an impulse radio two-waytransceiver, each electronic monitor M1 and M2 is a receive-only impulseradio. Precise, unsynchronized pulses are transmitted by the referencenetwork and received by the other reference impulse radio units R1-R4and the electronic monitors M1 and M2. The electronic monitors M1 and M2take these times-of-arrival (TOA) pulses, convert them to ranges, andthen determine their XYZ positions. Since the electronic monitors M1 andM2 do not transmit, only they themselves know their XYZ positions.

The reference impulse radio units R1-R4 used in this architecture areimpulse radio two-way transceivers, the electronic monitors M1 and M2are receive-only radios. The firmware for the radios varies slightlybased on the functions each radio must perform. For this design, thereference master impulse radio unit R1may be used to provide somesynchronization information to the electronic monitors M1 and M2. Theelectronic monitors M1 and M2 know the XYZ position for each referenceimpulse radio unit R1-R4 and as such they may do all of thesynchronization internally.

The data-rates between each radio link is a function of severalvariables including the number of pulses integrated to get a single bit,the number of bits per data parameter, the length of any headersrequired in the messages, the range bin size, and the number of impulseradios in the network.

For this architecture, the reference impulse radio units R1-R4 transmitin a free-running (unsynchronized) manner. The oscillators used on theimpulse radio boards often drift slowly in time, thus requiringmonitoring and adjustment of synchronization by the reference masterimpulse radio unit R1 or the electronic monitors M1 and M2 (whomever isdoing the synchronization). The accuracy of this synchronization(timing) is dependent upon several factors including, for example, howoften and how long each radio transmits.

The purpose of the impulse radio positioning network is to enable thetracking electronic monitors M1 and M2. Tracking is accomplished bystepping through several steps. The first step is for the referenceimpulse radio units R1-R4 to begin transmitting pulses in a free-running(random) manner. Then, when a electronic monitor M1 or M2 enters thenetwork area, it begins receiving the time-of-arrival (TOA) pulses fromthe reference radio network. These TOA pulses are converted to ranges,then the ranges are used to determine the XYZ position of the electronicmonitor M1 or M2 in local coordinates using a least squares-basedestimator. If the situation warrants and the conversion possible, thelocal coordinates can be converted to any one of the worldwidecoordinates such as Earth Centered Inertial (ECI), Earth Centered EarthFixed (ECEF), or J2000 (inertial coordinates fixed to year 2000).

Mixed Mode Tracking Architecture

For ease of reference, in FIGS. 22-27 the below legend applies.

Symbols and Definitions

Receiver Radio (receive only)

X Transmitter Radio (transmit only)

Transceiver Radio (receive and transmit)

R_(i) Reference Radio (fixed location)

M_(i) Mobile Radio (radio being tracked)

Duplex Radio Link

Simplex Radio Link

TOA, DTOA Time of Arrival, Differenced TOA

Referring to FIG. 22, there is illustrated a diagram of an impulse radiopositioning network 2200 utilizing a mixed mode reference radio trackingarchitecture. This architecture defines a network of reference impulseradio units R1-R6 comprised of any combination of transceivers (R₁, R₂,R₄, R₅), transmitters (R₃), and receivers (R₆). Electronic monitors(none shown) entering this mixed-mode reference network use whateverreference radios are appropriate to determine their positions.

Referring to FIG. 23, there is a diagram of an impulse radio positioningnetwork 2300 utilizing a mixed mode mobile apparatus trackingarchitecture. Herein, the electronic monitors M1-M3 are mixed mode andreference impulse radio units R1-R4 are likely time-synched. In thisillustrative example, the electronic monitor M1 is a transceiver,electronic monitor M2 is a transmitter, and electronic monitor M3 is areceiver. The reference impulse radio units R1-R4 can interact withdifferent types of electronic monitors M1-M3 to help in thedetermination of the positions of the mobile apparatuses.

Antennae Architectures

Referring to FIG. 24, there is illustrated a diagram of a steerable nullantennae architecture capable of being used in an impulse radiopositioning network. The aforementioned impulse radio positioningnetworks can implement and use steerable null antennae to help improvethe impulse radio distance calculations. For instance, all of thereference impulse radio units R1-R4 or some of them can utilizesteerable null antenna designs to direct the impulse propagation; withone important advantage being the possibility of using fewer referenceimpulse radio units or improving range and power requirements. Theelectronic monitor M1 can also incorporate and use a steerable nullantenna.

Referring to FIG. 25, there is illustrated a diagram of a specializeddifference antennae architecture capable of being used in an impulseradio positioning network. The reference impulse radio units R1-R4 ofthis architecture may use a difference antenna analogous to the phasedifference antenna used in GPS carrier phase surveying. The referenceimpulse radio units R1-R4 should be time synched and the electronicmonitor M1 should be able to transmit and receive.

Referring to FIG. 26, there is illustrated a diagram of a specializeddirectional antennae architecture capable of being used in an impulseradio positioning network. As with the steerable null antennae design,the implementation of this architecture is often driven by designrequirements. The reference impulse radio units R1-R4 and the mobileapparatus A1 can incorporate a directional antennae. In addition, thereference impulse radio units R1-R4 are likely time-synched.

Referring to FIG. 27, there is illustrated a diagram of an amplitudesensing architecture capable of being used in an impulse radiopositioning network. Herein, the reference impulse radio units R1-R4 arelikely time-synched. Instead of the electronic monitor M1 and referenceimpulse radio units R1-R2 measuring range using TOA methods (round-trippulse intervals), signal amplitude is used to determine range. Severalimplementations can be used such as measuring the “absolute” amplitudeand using a pre-defined look up table that relates range to “amplitude”amplitude, or “relative” amplitude where pulse amplitudes from separateradios are differenced. Again, it should be noted that in this, as allarchitectures, the number of radios is for illustrative purposes onlyand more than one mobile impulse radio can be implemented in the presentarchitecture.

From the foregoing, it can be readily appreciated by those skilled inthe art that the present invention provides a system, electronic monitorand method for monitoring whether the person under house arrest stayswithin or around their home. In another embodiment of the presentinvention there is provided a system, electronic monitor and method fortracking the location of a person within their home and/or monitoringthe vital signs of that person. Also, the present invention enablesmonitoring personnel to communicate with or eavesdrop on a person.

Although various embodiments of the present invention have beenillustrated in the accompanying Drawings and described in the foregoingDetailed Description, it should be understood that the invention is notlimited to the embodiments disclosed, but is capable of numerousrearrangements, modifications and substitutions without departing fromthe spirit of the invention as set forth and defined by the followingclaims.

What is claimed is:
 1. A system comprising: an ultra wideband impulseradio transmitter capable of transmitting an impulse radio signal andfurther capable of being attached to a person under house arrest; anultra wideband impulse radio receiver capable of initiating an alarm formonitoring personnel located near a central station whenever the ultrawideband impulse radio receiver fails to receive the transmitted impulseradio signal indicating that the person has moved out of a receivingrange of the ultra wideband impulse radio receiver; and a plurality ofreference ultra wideband impulse radio units distributed at knownlocations within or near a home, wherein said central station is furthercapable of displaying a current position of the person within or nearthe home that was determined from the interaction between the ultrawideband impulse radio unit and at least two of the reference ultrawideband impulse radio units.
 2. The system of claim 1, wherein saidultra wideband impulse radio transmitter is an electronic monitor.
 3. Amethod for tracking a person under house arrest, said method comprisingthe steps of: attaching, to the person, an ultra wideband impulse radiotransmitter capable of transmitting an impulse radio signal; andalerting monitoring personnel located near a central station that theperson is no longer within a receiving range of an ultra widebandimpulse radio receiver whenever the ultra wideband impulse radioreceiver fails to receive the transmitted impulse radio signal;determining a current position of the person within or near a home byenabling the ultra wideband impulse radio unit to interact with aplurality of reference ultra wideband impulse radio units that aredistributed at known locations within or near the home; and displaying,at the central station, the current position of the person within ornear the home.
 4. The method of claim 3, further comprising the step ofalerting monitoring personnel that the person has tampered with theultra wideband impulse radio transmitter.
 5. The method of claim 3,wherein said ultra wideband impulse radio transmitter is an electronicmonitor.
 6. An electronic monitor comprising: a fastening mechanismcapable of attaching said electronic monitor to a person under housearrest; an ultra wideband impulse radio transmitter, coupled to thefastening mechanism, capable of transmitting an impulse radio signal toan ultra wideband impulse radio receiver that is capable of alertingmonitoring personnel whenever the ultra wideband impulse radio receiverfails to receive the transmitted impulse radio signal; and said ultrawideband impulse radio unit is operable to interact with a plurality ofreference ultra wideband impulse radio units such that monitoringpersonnel can track the position of the person within or near a home,wherein the position of the person is determined by: synchronizing thereference ultra wideband impulse radio units; synchronizing the ultrawideband impulse radio unit to the synchronized reference ultra widebandimpulse radio units; collecting and time-tagging range measurementsbetween the ultra wideband impulse radio unit and at least two of thereference ultra wideband impulse radio units; and calculating theposition of the person within or near the home carrying the electronicmonitor containing the ultra wideband impulse radio unit using thecollected and time-tagged range measurements.
 7. A method for trackingand monitoring a person under house arrest, said method comprising thesteps of: attaching, to the person, an ultra wideband impulse radiounit; determining a position of the person within or near a home fromthe interaction between the ultra wideband impulse radio unit and atleast two of a plurality of reference ultra wideband impulse radio unitsdistributed at known locations within or near the home; receiving, at acentral station, information from the ultra wideband impulse radio unitrelating to the person; displaying, at the central station, at least aportion of the information relating to the person including the positionof the person within or near the home; and using the ultra widebandimpulse radio unit and another ultra wideband impulse radio unit at thecentral station to establish two-way communications between monitoringpersonnel at the central station and the person, wherein the ultrawideband impulse radio unit is used to determine the position of theperson and also used to establish the two-way communications between themonitoring personnel and the person.
 8. The method of claim 7, whereinthe information relating to the person includes a monitored vital signof the person.
 9. The method of claims 7, wherein at least one of saidreference ultra wideband impulse radio units further supports an ultrawideband impulse radar operation which enables the at least onereference ultra wideband impulse radio unit to sense the movement ofanother person not carrying an ultra wideband impulse radio unit withinor near the home.
 10. The method of claim 7, further comprising the stepof determining a position of the person located outside the home usingGlobal Positioning System (GPS) based technology.
 11. The method ofclaim 10, wherein said step of determining a position of the personlocated outside the home using GPS based technology further includestracking the person.
 12. The method of claim 7, wherein said step ofdisplaying further includes indicating an alarm whenever the personroams outside of the home.
 13. The method of claim 7, further comprisingthe step of indicating an alarm, at the central station, whenever theperson tampers with the ultra wideband impulse radio unit.
 14. Themethod of claim 7, wherein said step of using further includes enablingthe monitoring personnel using the central station to eavesdrop on theperson.
 15. The method of claim 7, wherein said step of using furtherincludes enabling the monitoring personnel using the central station tonotify the person that a rule has been violated.
 16. The method of claim7, wherein said step of using further includes enabling the monitoringpersonnel using the central station to verify the identity of the personusing voice recognition technology.
 17. The method of claim 7, furthercomprising the step of coupling a sensor to the ultra wideband impulseradio unit, wherein the sensor is capable of monitoring at least onevital sign of the person.
 18. The method of claim 7, further comprisingthe step of determining a position of the person within a workingenvironment using ultra wideband impulse radio technology.
 19. A systemcomprising: an electronic monitor, attached to a person under housearrest, including an ultra wideband impulse radio unit capable oftransmitting an impulse radio signal containing information relating tothe person; a plurality of reference ultra wideband impulse radio unitsdistributed at known locations within or near a home at least two ofwhich interact with the ultra wideband impulse radio unit to enable thedetermination of a position of the person; a central station capable ofobtaining the information and further capable of displaying at least aportion of the information relating to the person including the positionof the person within or near the home; said central station including anultra wideband impulse radio unit that interacts with the ultra widebandimpulse radio unit attached to the person to establish two-waycommunications between monitoring personnel at the central station andthe person, wherein the ultra wideband impulse radio unit attached tothe person is used to determine the position of the person and also usedto establish the two-way communications between the monitoring personneland the person.
 20. The system of claim 19, wherein said electronicmonitor further includes a sensor capable of monitoring at least onevital sign of the person.
 21. The system of claim 19, wherein at leastone of said reference ultra wideband impulse radio units furthersupports an ultra wideband impulse radar operation which enables the atleast one reference ultra wideband impulse radio unit to sense themovement of another person not carrying an electronic monitor within ornear the home.
 22. The system of claim 19, wherein said central stationis further capable of displaying a position of the person locatedoutside the home using Global Positioning System (GPS) based technology.23. The system of claim 19, wherein said central station is furthercapable of alerting monitoring personnel whenever the person roamsoutside of the home.
 24. The system of claim 19, wherein said centralstation is further capable of alerting monitoring personnel whenever theperson tampers with the electronic monitor.
 25. The system of claim 19,wherein said monitoring personnel using the central station are capableof eavesdropping on the person.
 26. The system of claim 19, wherein saidmonitoring personnel using the central station are capable of notifyingthe person that a rule has been violated.
 27. The system of claim 19,wherein said monitoring personnel using the central station are capableof verifying the identity of the person using voice recognitiontechnology.
 28. The system of claim 19, wherein said central stationfurther comprising the step of determining a position of the personwithin a working environment using ultra wideband impulse radiotechnology.
 29. An electronic monitor comprising: a fastening mechanismoperable to attach said electronic monitor to a person confined to ahome; a sensor operable to monitor at least one vital sign of theperson; an ultra wideband impulse radio unit operable to interact withsaid sensor such that monitoring personnel can monitor the at least onevital sign of the person; said ultra wideband impulse radio unit isoperable to interact with a plurality of reference ultra widebandimpulse radio units such that monitoring personnel can track theposition of the person within or near a home; and an interface unitoperatively coupled to said wideband impulse radio unit which interactswith a remote central station including an ultra wideband impulse radiounit to establish two-way communications between monitoring personnel atthe central station and the person, wherein the ultra wideband impulseradio unit attached to the person is used to determine the position ofthe person and also used to establish the two-way communications betweenthe monitoring personnel and the person.
 30. The electronic monitor ofclaim 29, wherein at least one of said reference ultra wideband impulseradio units further supports an ultra wideband impulse radar operationwhich enables the at least one reference ultra wideband impulse radiounit to sense the movement of another person not carrying an electronicmonitor within or near the home.
 31. The electronic monitor of claim 29,further comprising a Global Positioning System (GPS) receiver capable ofinteracting with a plurality of GPS satellites such that monitoringpersonnel can track a position of the person located outside the home.32. The electronic monitor of claim 29, wherein said interface unit isoperable to sound an alarm whenever the person roams outside of thehome.
 33. The electronic monitor of claim 29, further comprising aninterface unit is operable to sound an alarm wherever the person tamperswith the electronic monitor.
 34. The electronic monitor of claim 29,wherein said interface unit enables monitoring personnel to eavesdrop onthe person.
 35. The electronic monitor of claim 29, wherein saidinterface unit enables monitoring personnel to verify the identity ofthe person using voice recognition technology.